I have all those books, and have had them for well over a decade in some cases. They're very interesting, and often have some really nice illustrations, especially Angus McBride's covers. They're very exhaustive, but there are a couple of things to remember about them:
* Much of what they detail is purely speculation or outright creation on the part of ICE. While this was necessary in regards to providing info for MERP, it can be tough to determine what was taken directly from Tolkien, and what ICE created.
* In addition, some of ICE's interpretations of people and things are often ridiculously overpowered. I mean, I have my power-gaming moments, but still... Plus, everything is given a bonus of some kind, often with little rhyme or reason. The Ring of Barahir, for example, is given powers against dragons. This makes some sense, but there is nothing to indicate this is so in the books that I've seen. It could well be that it was simply a non-magical heirloom, just as the Elessar may have been.
I guess the only reason I have any qualms about any of this is that some of ICE's stuff may be taken as canon, or coming from canon, when it isn't or hasn't. It can mess up people trying to do conversions of the books for other games. That's why I have stayed away from using these books while doing my own conversions; I only use Tolkien's books and Foster's "Guide." But that's just my own personal taste. All in all, though, they're great to have, and you can see the writers did some deep research for them, and really loved the subject matter.