Creating Magickal Entities is a comprehensive reference manual that presents step-by-step instructions for creating entities through astral manipulation that will change your life. This manual, written by three practicing occultists, reveals magickal and alchemical methods, many which have been lost and suppressed through the ages, in a refreshingly modern way that magickal practitioners of any tradition can understand.
Relatively framework agnostic, although the examples given are quite narrow; in particular if you're not into numerology, seems you have to do a lot of adapting. Definitely not an entry level text. Has that same 'with proper determination and dedication to your task, anything will be possible for you' optimism you get with old fitness books, which is pleasant. Cannot speak on whether advice is practically effective; have not attempted any of it thus far (will update if I ever create an entity). Finally, the appendices where the authors talk about entities they've created is strong nerd shit. No disrespect to them but based on the appendices alone these people do not sound cool.
Short, simple, and to the point. I would have liked more examples, although perhaps I'm being a bit greedy because there are several in the appendix at the end. This assumes the reader already has magickal experience (which I would recommend anyway -- creating an entity is basically doing all the 101 stuff on the next level).
The only drawback is that they relied heavily on numerology as their suggestion for naming and "physically" designing your entity. I'm not well-versed in numerology, so I'm probably going to adapt it. I just wish they'd been more generic.
Some good info and ideas for inspiration; amateurish in execution (not necessarily in a bad way), the poor editing is distracting. Not a bad little introduction to the topic.