I'm in the process of reading Adler's book now, and I've found it's pretty bootstrap-able. I've been able to apply the lessons as I go along, and I've even gone back to earlier sections and increased the "resolution" of my understanding so to speak by applying later techniques.
Any PL related material you'd recommend as a prerequisite for these materials? I don't have a formal CS background, but I do have a few years' professional experience.