Basic Product Management
A hitchhiker's guide to product management - Yulin Zhang
A huge compendium explaining the requirements and skills of product managers, with plenty of links for further reading.
The role of a product manager - Michael Siliski
A nice distillation of the role of a PM based on Ben Horowitz's writings.
How to build successful products in a digital world - Nikkel Blaase
Astutely breaks down product creation into three distinct parts of a product's lifecycle: problem-solution fit, product-market fit, and distribution-conversion fit.
Doing random crap does not work - Jon Westenberg
"You need to be able to see where you're going and know how to get there."