I have written two books so far and have a third outlined. They are marketing ideas and how-to books. I made a few thousand euro from them so far(They still sell) but perhaps more importantly they helped open a few awesome doors for a me a couple of months ago when I was looking for a job. I ended up with some great job offers.

I wrote up 12 things i learned from my first book here: http://beautiful-email-newsletters.com/books/12-things-i-lea...

For my second book the learning was about making time to aggressively market the book and having a plan in place. I found after the hard work of writing the book I did not have the energy to do the marketing straight away. I should have taken a break before launching.