Right now as I'm in mushing withdrawal I'm re-reading "Running With Champions - A Mid-Life Journey on the Iditarod Trail" by Lisa Frederic. It's a great book about how she got involved with sled dogs and ended up running one of Jeff King's teams in the Iditarod. There's a great quote in that book, she doesn't name who it was that said it to her but I love it. "Beware of mushers, they will suck you into their addiction" So true!
I'm also anxiously awaiting the arrival of "The Speed Mushing Manual: How to Train Racing Sled Dogs". I found it on eBay and had to buy as in a sled dog forum discussion about books it comes highly recommended. One musher referred to that and one other book as his "bibles".
Anyone who likes mysteries and horses should check out the Dick Francis series. I've got tons of his books and really enjoyed them. And those who prefer less mystery, more wild and raunchy behaviour but still centered around horse sports will like Rita Jefferies books "A Dark Horse" and "Out of Control". Also Jilly Cooper is a good author and some of her books characters are show jumpers and polo players.