you said you thought the LoF books were a hoot, but my eyes glazed over and my brain went slack when I browsed it! We are dealing with a rock-bottom math person trying to guide a mathy kid here!!
I thought I wasn't mathy either until I signed up for the Living Math forum and over the years have been relearning math through the math literature books listed on the forum owner's website. Math stories are a great way to learn/relearn math. I now find that I do have some math ability and because I'm learning it from stress-free stories vs. textbooks, my interest in math has soared and I'm able to keep up somewhat with my very mathy son's interests. I strongly recommend the Living Math forum and website for those who haven't heard of them:
http://www.livingmath.net/ (go to reader lists tab for booklists organized by math topic)
http://groups.yahoo.com/group/LivingMathForum/I also strongly recommend the Murderous Maths series. My son, who loves Life of Fred, finds MM even more of a hoot.
Visit the official site for more cool stuff:
http://www.murderousmaths.co.uk/I've found that the Book Depository offers more competitive prices for buying them new (shipping is free worldwide):
http://www.bookdepository.com/search?searchTerm=murderous+mathsThis is only personal opinion. I don't profit by recommending these books. Good luck!
