Book · Book, about 200 pages
The SaaS Playbook: Build a Multimillion-Dollar Startup Without Venture Capital
Rob Walling · MicroConf Paid Beginner
Walling bootstrapped five companies, so this is the rare GTM book written by someone who never had money to waste. The marketing and pricing chapters are specifically about picking one or two channels you can afford and grinding them, which is exactly the constraint a bootstrapped founder is under.