I've done marketing for startups for many years. Growth Hacking (mentioned in previous comments) is a pretty decent framework. Also, if you had to read only one book, I'd recommend 'Lean Analytics'. It'll help you structure your thoughts and prioritise. (Note: I am not related to the authors or publishers) Other than that, take the businesses you like most, and check out their social pages, their blog, etc. Sign up for their newsletter. Figure out what they communicate, how, when, etc. Last but not least, marketing involves a lot of common sense. Good luck with the journey!