As with the first game in the series, there exist books and magazines to improve weapon durability. But I don't know how these interact with the combo weapons, if at all. Has anyone experimented with this yet?
There are magazines which improve the durability of the base items, such as sports, construction, entertainment, and toy items but, it doesn't look like there is any books that improve the durability of combo weapons. Weapons that are improved have a small green book icon on the lower right corner of the weapon icon, and the durability affect is stackable (ie. having a book that improves bladed weapons, and a book that improves sports items, will make broadswoards, and battleaxes durability increase 9 times that of normal, as each book triples the durability, and they stack).
From what I have played of DR2, if you have a book/magazine that gives +10% PP for a kill with a melee weapon (for example), then it gives you this bonus on top of what you get with using combo weapons.
So, if you run around with a spiked club (baseball bat + nails (the first combo card you get)), and also have the weapon magazine from the Yesterday, Today, Tomorrow stall, you get either 55 PP for a normal kill, or 220 PP for a 'special' kill with the spiked club.
Combo weapons are affected by magazines, yes. For example, some people suggest loading up on durability magazines and riding around on the slicecycle for the 72,000 zombie kills. With enough magazines, you can make it near indestructible meaning you don't have to waste time making a new slicecycle as often as usual.