I've got a couple I borrowed here and one is something I will buy and the other not so much. Do not bother with Penang Discus by shaifullah. Though it has SOME good reading allot of it you can learn right here on SD. The other is the trophy discus by dick au, and I like this one as it describes each strain in detail, how it was created and what you get when you cross it with or back to other strains. HTH