Things to think about:
What sort of books – will they need much design work putting in? Can you do this? If some is needed and you have to pay for it, it might cost a bit – can you afford to stump up the money up front.
How many are you going to print? Where? What will happen if you can’t/don’t sell them – is there a shelf life on the book?
Can you distribute/market them yourself? Who to? Do you have any contacts for big shops or are you aiming at local places? Have you got the time and resources to do this? You’ll need to knock up some sort of info sheet on the book if you want to get sales in advance.
Is there definitely a market? The ‘outdoor book trade’ isn’t massive… Is you book different to any others out there? Is there anything about to come out that’s similar to it?
These are all things a publisher would handle for you – takes all the risk away from you.
I’ve not self-published stuff, but I have worked for a small publishing company (outdoor industry-focused).