Andrew Chen's blog is probably the most relied source when it comes to learning about metrics like CAC and LTV. For real life case studies, follow Nathan Latka's podcast to know what each of these mean for different startups in different industries.
Growth Hacking is ever evolving and hence what worked in the past may not work in the future. But they are still good resources to learn about what worked in the past. Two books that I can recommend are:
1. Viral Loop
2. Traction

You can ask me any follow up questions that you may have.