How to find a sellable subject for an ebook

How to Write an Ebook: Choose a Sellable Topic

Read the How to Write an Ebook: The Guide and How to Write an Ebook: Why It's a Good Idea here.
So you've decided to write an ebook and you've got a designated spot in your schedule to work on it.

What should your ebook be about?

Be strategic about the topic of your ebook. This is not necessarily a "write whatever and they will come" sort of endeavor. A little research is helpful, as is some serious thought.
When choosing a topic, think PFC:

P – Solve a Problem. I know I've said this about 15 million times on this blog, and I apologize for being a broken record, but seriously, be helpful! "How to" topics are excellent choices for ebooks. Find a hole and fill it. The hole you find doesn't have to be huge, it's just gotta be common to at least a decent-sized group of people.
F – Address a Fear. Most of us have fears and we do our very best to avoid them. Our fears range from "What are people going to think of me?" to "What if my spouse gets cancer?" to "What if we run out of money?" to "What if I die?" to "What if my children turn out to be tyrants?" and on and on. So, if you can come up with a topic that addresses a common fear and you offer a way to relieve that fear, you just might have a winner of a topic.
C – Satisfy a Curiosity. People wonder about stuff. This is why celebrity gossip is so popular and why reality shows are captivating. What's it like to live in a family of 19? How does so-and-so run his business successfully? Who's going to be wearing what at the Oscars? You get the picture. The bottom line is, we are intrigued by information that's not readily available. If you have an inside peek into something the masses might like to know (and are free to share that information), it might be a good ebook topic.

Now, if you can kill two birds with one stone (with PFC) and figure out how to effectively include two of the three in your ebook, all the better. I'm sure there are even some of you creative minds who will figure out how to solve a Problem, address a Fear and satisfy a Curiosity all in one shot. May you become ebook superstars!
In my case, I tried to tackle both the P and the F. In Tell Your Time, I address the fear of living a luckluster life with the how of managing your time in a simple, straightforward 4-step way.
Here are some additional things to think about when choosing an ebook topic:

1. Write about something you've got a passion for or at least know a fair amount about.

Once your ebook is launched, people are likely to ask questions about your topic. If you're writing it just to make a quick buck but you know nothing about the subject, things will fizzle when you can't answer their questions. Or, you'll be frustrated having to answer questions about something you could care less about.
If others ask your advice on a subject, that's often a clue that you have something great to offer (even if you don't feel like a ninja).
For me, I enjoy organizing and most of all, efficiency. So, an ebook on time management wasn't a stretch at all. I also had already gotten positive feedback on the information so it made me confident that others might find it helpful as well.

2. Choose a topic that has some meat and substance.

I read somewhere that an ebook should be at least 25 pages long. I'm not exactly sure who came up with that figure, but it seems reasonable to me.
What you don't want is a topic that could really be covered in about 10 pages and then you just use a bunch of filler to expand it to 25 pages so you can call it an ebook. If your topic can be sufficiently described in less than 25 pages, write a blog post, a blog series, a guest post or perhaps an ebooklet (in which case you should sell it for much cheaper).
I'm dancing on the line of this one with Tell Your Time coming in at about 28 pages. However, this was somewhat purposeful in that I was deliberately trying to keep it succinct to align with my Unique Selling Proposition (i.e. a book on time management that wasn't time consuming).

3. Write about something that fits with your established online identity.

So, for example, if people know you as the woman who is an expert knitter, your ebook will be easier to sell if it has something to do with knitting (or a topic somewhat closely related). If, however, everyone knows you as the expert knitter but you write an ebook about investing in the stock market, it's going to be a harder sell.
The exception to this would be if (a) you want to break into the "investing in the stock market" niche and you're going to use your ebook as a way to do that or (b) if, for some reason (maybe you mentioned it inadvertently in a blog post at one point), you have gotten a BOATLOAD of questions about investing in the stock market and since it doesn't really fit into your regular blog, you decide to write an ebook about it so you don't have to keep answering all the questions individually.
I sort of found myself in this situation. Obviously, my site is about blogging, but one day I threw up some tips about saving time using Gmail. Well, those tips turned out to be some of my most popular posts. While time management didn't quite fit in the "blogging for money" niche, it was somewhat related and was a feasible diversion in ebook form.

4. Have your target audience in mind before you begin.

This is related to the previous point, but the gist of it is, make sure you have a group of people in mind that you will market your ebook to. Who will want to read it? Would they be willing to pay you for it? The ability to put yourself in your potential reader's shoes will make writing much easier and your finished product better.
The size of your target audience matters too. I don't think you have to appeal to everyone on earth — by no means — however, if you'd like to write an ebook about ancient Mongolian tribal burial rituals, it'd be good to know if there are a whole lot of people who share your interest before you dive in. Do you have a market at all?
Also, does your target market spend much time online and therefore would be likely to (a) find your ebook and (b) know how to access it? Ebooks are still an enigma to many people so keep that in mind when choosing your topic. For example, ebooks targeting older populations are going to be trickier to sell than those targeting the 18-24 crowd simply because the older crowd (not all though!) are less internet savvy.
For me, time management is something everyone deals with, so I went big on this one.

5. Make sure the information is something they can't easily get for free elsewhere.

You may have heard people say "there's nothing new under the sun" which is largely true. In other words, most of the information we come across really isn't anything new, just packaged differently. So, in that sense, it's doubtful any of us will ever come up with a completely and totally novel idea.
Still, make sure your ebook is unique enough that someone isn't able to find it for free elsewhere without too much effort. And if your ebook content could be found elsewhere, have a solid Unique Selling Proposition. That is, make sure before you get started that you have a strong case why someone should shell out cash for your product and not just get the information for free someplace else.
In my case, time management books and blogs abound. One thing I've noticed about them though, is that so many of them are heavy on theory, overwhelming and (ironically) time consuming. In response, I made Tell Your Time short and to the point. I also came up with the tagline "What if you could change your life in less than 30 pages?" I wanted people to see that it was different right off the bat.