He isn't writing the book; he just said he's thinking about reading an already existing book about it to the kids on his football team that he coaches. The book is called "It's Just a Plant" and actually is pretty helpful in explaining cannabis and it's consumption by adults to a child just as one would explain alcohol to a child.
also, isn't a huge part of 'the drug problem' education? this reminds me of people who think abstinence-only sex education works. shielding kids from things like sex and weed only really hurts them in the long run, they'd be better off if they are educated about the facts, including the dangers, of smoking weed at a young age the same way they are taught about sex (well... in normal places at least).
i'd hate to see something like this torn down just because Snoop is behind it and because of his reputation or history... even if he is going to write a kids book how about we see what his motives are and what the book is actually like before writing him off in a 'lol snoop is so high, trying to get kids to smoke weed' fashion.
EDIT: obviously there are some caveats to this, i dont think you should necessarily be teaching 5-year olds about weed as soon as they start school, but writing off the whole idea without at least considering some possible positive effects is stupid.