Honestly, I "learned" FCP X by simply RTFM 😉
Printed the manual to pdf, so I can read it on my old iMac (not supported - FCP X runs, but slow and no effects 🙁 ), while fiddling around in FCP on the MBP
I'm afraid there aren't too many many books out on FCP X (yet). Most tutorials seem to be published as videos nowadays.