I agree with Clark, multiple and current manuals are required. Before working up any new load I want a reference in at least two manuals. What if your sole manual is a missprint? Your in deep Kimchee about .5 seconds after you pull the trigger.
I will comment on a trend in all the "new" manuals, they are all conservative and the loads have backed of by at least 5%. There are a couple of reasons for this, #1 is the loads are all pressure checked in actual guns and test barrels, they no longer rely on very good mathmatical guesses on pressure. #2 is the new manuals are a lot more product liability conscience, the don't publish close to or right at max loads anymore.
Good manuals: No reloading library should be without Ken Waters book on Pet Loads, I consider this a must have. I would also recommend the new Sierra Manual its a little pricey but if you load a lot of rifle cartridges its almost a requirement, a plus is the pistol load section. Other manuals I use a lot are my Hornady, and my Speer manuals. Another I use a lot is my Hogdon manual.
It isn't a reloading manual exactly but the NRA published a cartridge specification book, it has the best pressure information, a few handloads, good trim length and COL data. Bad news is I think it is out of print and has been for a while I didn't see it in the NRA store. Worth the hunt as I consider this one of my valuable handload library reference books.
Ok, now lets save you some money and help your reloading library. Most of these are free or cost under a dollar, and are updated almost every year.
Accurate Reloading Manual
VIHTAV ( available Online print it out )
Hercules/Alliant Powders Manual
Dupont (IMR) printed and available on line
There are several other powder manuals, almost every powder manufacturer makes this data available for free or close to nothing.
Other Manuals I use regularly:
Hornady
Nosler
Speer #4, #8, #9 ( I like my OLD Speer manuals better than the new ones)
Lyman- best for cast bullet data
Winchester- another Freebie or close to it ( look online)
Don't underestimate the Powder Manufacurers manuals this it top notch, thoughly tested data, and many times I find bullets or loads in these manuals that I can't find in other sources, just because it isn't expensive doesn't mean it isn't good.
I load a fair amount of wildcats, sources on these cartridges are a lot harder usually. It depends on the cat, some of the rarer cats are tough, my Speer #4 helps, but I keep reloading notebooks on these loads and cartridges. An example right now I am working on 404 Jeffrey loads, not in most manuals and it takes research.
On last word of caution MISTRUST all loads you get on line (excluding Powder Manufacturers) double check them, it doen't mean there wrong, just verify against a different source. If it looks wrong, or too hot don't use it. There are a lot of loads on line that are way over pressure, and some clown is cooking up some atomic loads, and swears he is getting normal pressure signs ( not that he knows how to read this). I frequent another board and I am seeing some loads on Ackley improved cartridges that are hotter than belted magnums. Two or three of these guys swear these are kosher loads. I and a couple of the other old handloading hands have our serious doubts, when somebody is claiming hotter loads with an improved case than I can get out of a magnum case with the same bullet. Also I caution stay away from duplex, and compressed loads until you are very experienced, these are dynamit when done wrong and very easy to make big Bo-Bo's.
Last I don't have it but this software (CD) will be my next udate to my reloading library:
http://www.gmdr.com/rcbs/rcbs.htm It seems to have a ton of data.
Hope this helps.