Also been loving "The Little Book of Talent" from the author of "The Talent Code" (which is another one of my favourite books).
And after reading a lot of Stoic philosophy over the years, I've finally got around to "A Guide to the Good Life". Very clear explanation of Stoic ideas so probably would have been the best place to start. :)
Other books I've really enjoyed are: Talent is overrated, by Geoff Colvin (short version: working hard is more than half the battle)
Drive, by Daniel Pink (short version: to be motivated, you need to have/be working toward purpose, autonomy, and mastery)
How will you measure your life, by Clayton Christensen (short version: just read it - very good)
For the win - how game thinking can revolutionize your business, by Kevin Werbach and Dan Hunter (Note: one of the authors offers a Gamification MOOC on Coursera)
And for fun:
Eastern Approaches, by Fitzroy Maclean (short version: a pseudo-biography about a british man who was a diplomat, politician, and special forces operator all in one lifetime. Incredible)
I've recently finished Dan Gilbert's: Stumbling on Happiness and I highly recommend it. It's witty and gives you a very different way of looking at what you think makes you happy.
I know these aren't start-up books, but unfortunately I haven't read any to recommend.
Like most people on HN probably would, I recommend reading Neil Stephenson's books, especially Cryptonomicon, The Diamond Age and Snowcrash (in order descending order of subjective of relevance).
http://www.andreaelectronics.com/pdf_files/Distant%20Sparks....