I've been reading up on secondary relationships, and it's pretty depressing stuff. If I'm interpreting it correctly, I should just be happy with whatever I can get, and should be grateful that the primary couple is letting me in at all. I'll admit that most of my ideas on poly come from Lazarus Long, so they're pretty idealized, but do all secondary relationships have to be shallow and, well, less? What is reasonable?
Welcome to the Forum Cat.
First of all the notions above strike me a load of codswallop. I'm unfamiliar with Lazarus Long, and I've never read Heinlein's works...however while SciFi is a vehicle to explore a lot of what-if's, it is a work of fiction. In order to explore alternate forms of sexuality, SciFi provides the opportunity to completely change the rules of society...so any poly context within those books will not necessarily resemble anything in the real world, depending on how much the rules have been changed.
The forum here has some great threads on secondary dynamics, negotiation, etc. Check out Master Thread - links to other threads worth reading or do a search for secondary and it'll open up a wealth of information for you.
At the end of the day you are a person, just like them...and deserve to be treated with love, integrity and respect, just like them. Everything else is negotiable.