It takes us 2-4 sessions to go through a book but we have a large group (8 players +GM). Our combat usually is over in 3-4 rounds. However we have had to take some steps to speed up combat so someone hasn't fallen asleep before it gets to be their turn again. These things include stuff like
1. No pets/familiars/summoned creatures etc. - With each player only controlling 1 thing on the map it helps things go quite a bit faster.
2. When it is the players turn they have 6 sec to start their action or else their character is considered to have a brain fart and looses his turn that round. - This keeps players paying attention and planing out what they are going to do before it is their turn.
3. Once you are done with your turn knock on the table. - This save a lot of sitting and watching until someone finally asks "Are you done?"
4. Implemented map tools. We had to go electronic. It was too hard to fit everyone around a map moving their guys and the GM asking everyone to move so he could reach around the map. With a electronic gaming table one of our guys built we eliminated that problem and it has sped up the GMs turns in combat considerably.
5. During combat your character (and thus you) can only speak on your turn. - This not only has lowered meta gaming but has also been a big time saver as people don't get distracted or taken down tangents.
6. Handle loot at the end of the session. Search/Appraise rolls are made after combat and it is assumed that the party took everything they could determine had value and wasn't nailed down. Details of the loot are not given until the end of the session unless it is needed to further the story. - This has also sped things along quite a bit. All the arguing of who gets what etc. takes place at the end and doesn't drag out combat or the story. It also makes it easy for the GM to have a printed list of all the possible loot and then take a magic marker and cross off the stuff we didn't find/get and just had it to the players at the end.
There are others but you get the idea. These might not be for you but they work for us. We had to make exceptions for all of us to be able to hang out together and play in the same game.
Try to analyze what is taking up the most time in your combat and make house rules to speed things up. I wouldn't make the rules alone though. Share your concerns and come up with solutions as a group. The gotcha that we found is that some rules can take away too much fun from the group. If that's the case change the rule or remove it and focus on a different area you feel will address your concern. In this case speed of combat.