10 lessons I've learned writting a book

Well, it was an anthology where I’ve gathered experts to ask one question (check it here). But it turned out to be more complicated than doing it alone. Anyway, these are the 10 lessons I’ve learned writing my book:
Who is it for? If you can’t answer it, start over.
What does this thing do? What problem are you solving with your book? Make it clear and build it from there.
Less is more. Always. It’s more difficult to write a 100-page book than a longer one. I left out a couple of chapters… That’s the price to pay.
It’s not about you. This is another lesson I learned with this blog. Think about adding value to the reader. She’s giving you a precious gift: attention. She’s choosing your book, with the opportunity cost that it implies.
At one point you’ve got to make a sacrifice. Books are about ideas. And ideas that don’t spread, die. This doesn’t mean you’ve got to lower you standards and make dumber writing. It’s about getting to the purest essence of your idea and find ways to make it spread.
First drafts suck. A book needs time to grow. Thankfully I had summer in the middle and I decided to turn the idea around. It needs time to be baked. Don’t rush a book, but keep in mind that you’ll need several drafts.
You better solve just one thing. Don’t try to solve a 1000 problems—just one. Solve a big problem and then identify the sub-groups within that problem.
Public deadlines work. Considering Parkinson’s Law—”work expands so as to fill the time available for its completion”—having a public deadline to ship it (especially when you self-publish) is a must–because your book will never be perfect, and you have to ship it one day.
When you publish it, start working on your next one. As Ryan Holiday says the best marketing for a book is to write another one.
PS. If you’ve counted them, you’d notice that there are only nine lessons. I didn’t do it on purpose, but interestingly that leads us to our tenth lesson: double check everything. Or triple check–because there are always something you’re missing!