Best sex education book for mature, questioning 10 yr old DS

[Solo2]

DS1 already has a lot of knowledge about sex and developing bodies, as I'm happy to answer all his questions and treat this subject as I would any other. For example, he'll ask intricate questions about physics and psychology, aerodynamics and intricate questions about sex - how it works, how bodies work, contraception, gay sex etc etc. In his mind, there's been no diffreence between these subjects. As far as I'm concerned, nothing is off limits except the intimate details of my own life!

He is now on the cusp of being embarassed yet wanting to have even more information - not in any kind of unhealthy, obsessive way but simply alongside a questioning personality and interest in all things. His body is just beginning to show sign of the very start of puberty and I assume he'll get more embarassed as the topic of sex becomes more pertinent to himself and his own developing physique.

I need a book that will give fairly detailed answers, possibly aimed at a higher age group - but nothing he can't handle emotionally of course. He knows all the basics and probably more than the average 10 yr old - though I have no idea what other 10 yr olds know!

Can anyone recommend something that takes him beyond the basics of 'birds and bees' and gives straightforward information that will be useful to him in future years?

[DOLLYDAYDREAMER]

hi - we have LETS TALK ABOUT WHERE BABIES COME FROM - WALKER BOOKS - FROM AMAZON - its not just about where babies come from - its starts quite basic & moves in sections onto more detailed & associated topics - so you can go through it in order & learn more as you go - it is a A4 size book with good illustrations.

[SecretSquirrels]

I found that the stuff they did in schools was not too helpful for my DS about the physical changes in boys. He complained that he had learned all about periods but nothing about boys bits. He was a very early developer at 10.
I found this one quite good. "Everything you wanted to ask about Willies and other boys bits" here
I gave it to DS1 when he was 10 or 11. There is stuff in there more for older boys but he was happy for me to pick out the chapters he should start with.