Welcome to the forum!
wrt library books on the kindle- your kindle will not natively support them. You would need to do some googling and find out how to strip DRM and then sideload them to your kindle. Some find it too complicated, some find it ethnically wrong and illegal, and some just don't want to bother. If you are set on reading library books on your ereader, Kindle may not be your best bet.
I'm not sure sure about the diagrams and such you are wanting. You can use Calibre to convert the format to one easily read by your kindle, but I don't know how well graphs and such would transfer over.
You'll definitely want to check out the Kindle Forum to talk to people who actually have kindles, but if it's just up to me, I'd say "yep, get a sony!" but I'm biased
