I can't recommend a book,but having two boys of my own,I'd suggest an on-going conversation,based more on values than mechanics.
Everything I've read,seen,heard and experienced has led me to believe that between school health class,bathroom talk etc..they get the mechanics.The "why you should wait" stuff has to come from YOU.Respect of your body,other people's bodies,seriousness of sex,consequences of sex(STD's,pregnancy,reputaion)all have to come from the parents,and that doesn't come in a book.
I've told my boys all along of changes in their bodies during puberty so when it does happen,that doesn't frighten them(my nephew freaked when he got hair "there" because he thought something was wrong with him).Just have a good relationship with your son,it's worth way more than the cost of a book.