have just started reading Framework Design Guidelines i must say that it's a must read for anyone who writes code that other developer may have to read or use. Framewroks designers, class library designers, plug ins, widgets etc... basically anyone who codes in .Net.
Its a VERY fast read, not a lot of overly conspetual stuff and very well written. Hopefully most of it is stuff you already do, fortunately i have worked with and been exposed to some very good coders and thankfully i have picked up their good practices so alot of this is confirmation of ideas.
Read it, you will either pick up lots of good practices or confirm you are doing things right. Either way its a book you can read in a weekend with out too much of a problem.