I am currently agent-free after a bad experience. I'm reluctantly looking for another agent but I've already sent Book 2 to the editor who published Book 1. Now don't bite me a big one, but if the editor wants Book 2, couldn't I just compare the new contract to the old one and ask for a little more of everything? Isn't that what a new agent would do? I'd really rather not be crushed by another ghosting agent.
Sure you could do that.
Do you know what's negotiable and what isn't?
Did your publisher include the new morals clause that's cropping up in lots of places?
Are you going to ask for revisions on the Force Majeure clause given the pandemic and supply chain issues?
You see my point.
Starting with the question of whether the contract for Book 1 was the best your agent could do (and I've seen some contracts that didn't appear to be negotiated at all), there could be lots of things that won't just be "ask for more."
I STRONGLY urge you not to try to do this yourself.
There are several ways to have contracts reviewed and negotiated by someone other than an agent. If you need names, drop me an email.
I'm sorry you had a bad experience with your former agent.
You might ask your editor for reccomendations on agents they like to work with. I've gotten more than one client that way.