You could certainly think of the offer letter as their opening offer in the negotiation process. It feels like it is there attempt to communicate "This is what we pay for this position" and hope that you aren't in a position or confident enough to make a counter-offer.
Things to ask yourself:
> How strongly do I want to work at this company and in this position?
> Based on a bit of research do I think this is a fair, market-competitive offer?
> Based on my own experience and compensation at current or recent jobs is this an enticing offer as it currently stands? Or am I feeling devalued by the offer?
Even if you are feeling good about the offer after answering those questions you should probably still make a counter-offer. If you feel really good about their offer you can make the counter more of a token - something that is easy for them to say yes to.
