I did an "adoption story" book for my DD. It talks about us pre-kids and her pre-us and then how we all came together to make a famly. I talk about her biological parents but not in great detail because I feel like it's something that we should talk about amongst us and not necessarily just put down my view of things in a book. And I wanted her to be able to share the book with others if she wanted to but still let her decide what she wants to tell people about some of the details. Reading through it always sparks some questions and conversation, though, which is good.
It's a tough balance because you don't want it to be all superficial "and everybody lived happily ever after" stuff, but there are different levels of things that you address about adoption over time as kids grow, so you can't just put everything into a book to share with, say, a 2 year old. I suppose there's always the option to add more pages over time?