We haven't tried the Cartoon guide yet but DS8 currently has the three books that ohmathmom posted (thanks by the way!) on his nightstand -
The Physics Book: From the Big Bang to Quantum Resurrection by Clifford Pickover, Albert Einstein and Relativity for Kids:...y Jerome Pohlen, and Isaac Newton and Physics for Kids: His Life and Ideas with 21 Activities Kerrie by Logan Hollihan.
All three have been a hit.
As mentioned Death by Black Hole was a big hit last year but we had to read it to him and I'll admit at times it made my head spin (and I like to think that I'm reasonably smart). DS is gifted/LD so his reading isn't as advanced as his science/math. It isn't a kids book but for an obsessed gifted kid it worked out.
We also have Cosmic Managerie (Mark A, Garlick) which is a beautiful astrophysics coffee table type book.
Lucy & Stephen Hawking's kid's books were also loved here.
The Nick and Tesla series was also a hit -
http://nickandtesla.com/