The Mom Test is a quick read, and will answer all these questions. The name comes from the idea that asking your mom what she thinks of your brilliant product concept is generally the opposite of what you should be doing. http://momtestbook.com
Thanks s1mon,
Have you used this concept in practice?
Not OP but I did, it's very helpful with a lot of practical advices.
I’ve worked in design and with/in startups for 25 years including 4 at IDEO. I’ve used techniques like the book explains, but before reading the book. The book is one of the better ones at introducing the right techniques (especially for SW products). So many startups and big companies ask the wrong questions, the wrong way and get useless answers. If you’re dealing with physical products, services or other things where the interaction with real spaces/things is important, this book might get you started, but others might be better.