It was recommended on this thread and sounds great but the description on Amazon sounds more like something aimed at adult men. I see it also has a chapter on 'girls', so need to check in case I get into trouble!
I got it for ds when he was 10, I think, or maybe just 11, and he loved it. I haven't actually seen the chapter on girls I have to admit, but it's such a dipping-into kind of book that I am certain an 8 year old would find chapters that interested him.
I should think the target market is 11-16+, plus nostalgic adults.
Whether it would suit an 8yo depends on reading level - my 8yo's a good reader and likes it very much (though not quite as much as Pick Me Up, also a recommendation from here, which he really loves).
The "girls" chapter in DBforB is sweet & super-sensible. It says: don't forget girls are people too, and after all not so unlike boys. If you want girls to like you, just talk to them. But you must also do some exercise, any kind of exercise, doesn't matter what but it must be something: don't underestimate the attractiveness of rosy cheeks.
My nephew liked it for his 7th birthday and he is actually not a very good reader - there was enough in there to get his attention, but it took a lot of input from his dad!
Agree with Bink about the girls chapter - it is absolutely fine.