Whenever I meet an aspiring PM, I'm asked, "Can you recommend any books or blogs to read?" Why, yes I can. Here are a few of my favorites:
Inspired, by Marty Cagan
It has one of the least imaginative names ever, but Inspired is the first and best book I've ever read on Product Management. Marty also runs a blog.
The Design of Everyday Things
Don Norman's classic is essential reading on design. His consulting company, Neilsen Norman Group, also has a phenomenal blog in which they publish the results of their UX studies and other invaluable (free) insights.
Intercom, the company responsible for the little blue chat icon on many of your favorite B2B products' sites, was founded by product managers who think deeply about the craft and share their thoughts and experiences with the world on their beautiful blog.
Blue Ocean Strategy
This book introduced me to thinking strategically about Products as drivers for business success, not just as beautiful, usable, user-facing things.
Crossing the Chasm
Like The Lean Startup and others, Crossing the Chasm provides a framework for thinking about your product over time rather than statically, because success should be measured differently at different stages of the product lifecycle.
Just Enough Research
Too many product teams fly by the seat of their pants, making arbitrary decisions on what to build based on what feels right or which customer is shouting loudest. Erika Hall lays out a simple framework for making better decisions with just a little effort.
Know what's going on.