Sorry can't remeber any books now, it was a long time ago, but I'm sure you can track some down. America seems to have more literature and stuff available then UK, and in fact we found it very hard to find any info in UK.
I think there is something called "joined Up Families" but I can't remeber much else.
The best ways round problems have beeen not to go in all guns blazing, but to say something like" I really need to talk to you about dd, and therre my be some stuff that you will find hard, but I need to say it"
Does he realise he is treating your dd differently? Also have to say, when we first moved in together, I was probably harder on my dss than on my ds. But it wasn't malicious or intentional, most of the time I didn't realise I was doing it. When I did I imeediately adjusted my behaviour. But I think some of it must be anthropological or whatever. Cavemen stuff, needing to protect your own genes or something.
Also, how long have you been together? It is meant to take a stepfamily 10 years to shake down together, much much longer than a normal family. The first two years are meant to be hell (and they were for us! awful!!)However we are now in year 5 and it has got a lot better. Having dd also helped unite us, AND, this is also something that I remember reading about. A baby can unite a stepfamily like nothing else, as you are all genetically tied and I have to say it is true for us.
HTH. There is something called stepfamilies UK, which is a bit like mumsnet, but I tend to avoid it as there is a lot of moaning and resentment about stepkids which I find a bit depressing tbh. I would hate my child to be resented just for existing