I just started this book this weekend and can't put it down. The only other work of Brin I've read is is graphic novel The Life Eaters. The practice Effect features a very Heinlein-esque hero. The competent scientist. The man who can puzzle out of any situation and do it with a certain panache. The hero Denis Neul, is a qunatum physicist who elects to explore an newly discovered reality. he discovers the world of tatir, populated by huimans who speak english. The one major difference is 'the practice effect'. In Tatir, a knife gets sharper the more you use it. Indeed, if you start with a stone knife it will become a crystal blade of impossible sharpness over time. This both enhances and criples the culture of Tattif, as nobody ever needs to invent anything. they just make rough caveman tools and practice them into perfection. I'll let everyone know how this one turns out its a lot of fun and i recommend it!