Pornified by Pamela Paul is a good book to read, as well as the Gail Dines book, but there is also some good social research on the net about porn and the early sexualisation of children. There are also lots of interesting threads on the Feminist board, but the angle that seems to receive little coverage is how users themselves are victims of the porn culture, especially the group I would describe as the "uninformed and don't want to know either", which encompasses a lot of users and their partners, I think.
It's pretty evident on here that lots of women believe that their partners occasionally look at fairly harmless porn and that women also look at it with their partners or on their own. However, with the advent of private browsing facilities to protect the forgetful - and the ability to delete history, for the more IT-savvy user, it occurs that many partners really haven't a clue what their partners look at in secret - and don't want to know either. This group doesn't want to know about the provenance of the porn or what the actors are forced to do, believing instead that a sizeable majority of porn stars make a free choice to be physically injured during the making of the films, especially because they "appear to be enjoying it" 
.
There are users who make active choices to seek out "ethical porn" where the actors are treated well and not exploited, but even then, I am sceptical about whether that is a truly informed choice and like all porn, it can nevertheless become addictive and de-sensitising to real-life sexual relationships. A daily habit is certainly an addiction.
The other issue I wanted to mention is that relationship therapists are now reporting links between excessive porn use and infidelity. Many partners of porn users seem to comfort themselves with the belief that porn is harmless self-relief and might actually prevent "real" infidelity, but the reverse appears to be true.
This is because like any addiction, a user needs an even greater "hit" after a while and the culture of secrecy, lies and illicit sexual behaviour connected with hidden porn addiction, paves the way to finding a real-life partner with whom to enact porn fantasies - hence the increase in no-strings-sex dating sites, escort use or infidelity, at the first opportunity.
This subject always attracts a lot of anger and derision from all sides of the debate, but as you rightly said, this is a support thread and what you need is help to negotiate some boundaries in your primary relationship. If you do this now, before your children become older, it will help you to parent them and protect them by having a porn-free house and a consistent and harmonious message from both of you later on, about porn. It really helps teenagers especially if both parents are delivering the same message and giving them information about their sexual choices. It also supports what secondary schools are trying to achieve.
On a general point about a relationship and any harmful behaviour that is negatively affecting it, I believe that stopping the behaviour on its own rarely works. Although "cold turkey" will defeat an addiction, sometimes other addictions will surface to replace it. It is therefore more sustainable if an addict makes the decision himself, after assessing the information. For you as his partner, that means stating your boundaries and any consequences that will happen if the porn use continues, but to enforce those choices, it follows that your partner needs to stop keeping secrets and telling lies, otherwise your choices will be denied.
Many couples have this showdown and then the non-using partner crosses their fingers and hopes for the best. Some stop loooking for evidence that will cause them to act on previously issued threats, hence the truth in the relationship becomes compromised by smoke and mirrors.
It's much easier to trust and believe someone if s/he shares the same views as you about the issue and speaks openly against porn and the effects we're seeing. I would also add that it becomes obvious during sex whether someone is a porn user, but have observed that there are lots of women on Mumsnet who have never had the opportunity to experience sex with someone who doesn't use porn - and that's a real shame 
.