Be very careful of publishers only offering a eBook contract. Usually, all they will do is upload to Amazon, and take a big percentage of your earnings, and own your copyright for a very long time. I don't know about audiobooks, so I won't comment on that. But I'd spend some time researching the publisher, to make sure they are not a fly by night operator. Maybe search for [publisher] [fraud][scam] etc.
Selling books is hard, and most publishers fail at this task (I've heard figures like one or two authors like EL James making the bulk of profits). Just having a good strategy isn't enough, as things that sound good on paper fail miserably in the real world.
I am going to disagree slightly with Standback's answer. I would not recommend hiring an agent. Make sure you have read Dean W Smith's articles on agents (and the one specific to agents and contracts). An English literature major is not qualified to give you advice on legal contracts.
The better idea is to higher a good IP lawyer. To start you off, the Passive Guy has written a good article on contracts:
Looking specifically at the clause I discuss here, I don’t believe any
responsible agent who understood the clause would permit her/his
client to sign a contract with such a clause included, yet many agents
have done that very thing
If agents are negotiating contracts and advising clients on the
meaning of those contracts or particular provisions of those
contracts, they’re doing work that attorneys do in non-literary
settings. Trained paralegals performing services in another field that
literary agents regularly perform with publishing contracts would be
charged with the unauthorized practice of law.
To summarise: Hire a good IP attorney to look at the contract.