Appendices B & C
I'm willing to bet there isn't a single reader of The Lord of the Rings that has never consulted Appendix B. With so much going on - and so much backstory - how can you not? "The Tale of Years" is an absolute necessity for keeping track of the complex plot layering within the story. In fact, not only is it a great resource for the three volumes that precede it but if you're reading The Silmarillion, Unfinished Tales or even The History of Middle-Earth series, this Appendix helps a reader keep his bearings.
While there is reference to the First Age of Middle-Earth and the Elder Days that come before, Tolkien had yet to organize and sift through the tons of material he had written of those periods. So it gets barely a mention. There is, however, a good fleshing out of the events of the Second Age which is kind of the Golden Age of both the Numenoreans and the Elves. Most of the events have already been discussed in Appendix A, but there are some notable entries not previously mentioned.
For example, the whole matter of the forging of the Rings of Power, as well as Sauron's One Ring, is recounted. A lot of readers wonder why the conflict between Sauron and his enemies dragged on so long after the One Ring was created. You have to keep in mind that, while both races of Elves and Men were at the height of their strength, the forces of good engaged Sauron only to the extent that they needed to. And it was only when the Numenorean realms in exile were established that Sauron felt the need to became more aggressive in countering this threat. It wasn't until the Last Alliance of Elves and Men that the conflict came to a showdown over control of Middle-Earth. Later on, by the time of the War of the Ring, Sauron had the advantage because most of the Elves have sailed West over the Sea and the strength of Men had dwindled down to what was left in Gondor.
The arrival of the Istari - the wizards - is also chronicled although it focuses primarily on Saruman and Gandalf. We see the kind of duplicitous actions that Saruman used in the Council of the Wise to allow him to gather his own power while he searched for the One Ring himself. It is also important to note that in the process Tolkien traces the histories of all the races and intertwines their dealings within this one chronology. So we can even see how the hobbits developed from three scattered "tribes" to a united group of little folk existing in the Shire, a region that evolved in the wake of the fall of Arnor.
As far as the War of the Ring goes, Appendix B explains exactly which events are taking place simultaneously throughout Middle-Earth on any given date. Within Tolkien's narrative, he leaves out a lot of this information to maintain the tension throughout the story. Frankly, it wouldn't be as interesting if the reader had the omniscience of knowing everything that was happening at once. It's part of the genius of how The Lord of the Rings is layed out. But with additional readings, it's nice to be able to grasp where Gandalf is as the hobbits trek through the Old Forest or what is going on with Aragorn, Gimli and Legolas as the City of Gondor is under siege.
The other bonus of Appendix B is that we can learn exactly what happened in Middle-Earth after Sam came home to the Shire from the Grey Havens. Interestingly enough, Tolkien converts the measurement of time at this point to that of the Shire Reckoning. We find out the final stories of each of the remaining members of the Fellowship - Sam, Merry, Pippin, Gimli, Legolas and King Elessar (as well as Arwen). In the year 1482 S.R., Rosie Cotton Gamgee dies and Sam (whose surname he has changed to Gardner) follows a fate befitting one who was once a Ring-bearer:
"On September 22, Master Samwise rides out from Bag End. He comes to the Tower Hills, and is last seen by Elanor, to whom he gives the Red Book afterwards kept by the Fairbarns. Among them the tradition is handed down from Elanor that Samwise passed the Towers, and went to the Grey Havens, and passed over the Sea, last of the Ringbearers."And it is on this premise - the preservation of the Red Book of Westmarch - that we are able to know and read the story of The Lord of the Rings.
Hobbits were known for their love of personal history as opposed to more general history. While they generally shared a lack of concern for the events of the broader world at large, they were intense about their knowledge of family trees. I suspect that Tolkien was also a genealogy freak. In the section "Family Trees" he goes to great lengths to show the lines of the Baggins', the Brandybucks, the Tooks and the Gamgees.
Frankly, unless you're a genealogy aficionado, this is one of the Appendices that you'll spend very little time on. I would, however, like to point out that having become familiar with the early drafts of "The Fellowship of the Ring" I noticed several of the original names that Tolkien had kicked around for Frodo, Sam, Merry and Pippin scattered among the family trees. Among these are Bingo, Odo, Falco (Folco), Fosco and Marmadoc (Marmaduke). Also if you took through the trees, you can find the familial relationship between not only Bilbo and Frodo, but of Merry and Pippin to the two Baggins'.
Bilbo is referred to as Frodo's cousin in the books and as Frodo's uncle in the films. According to Tolkien, both Bilbo and Frodo trace their families back to one common ancestor, Balbo Baggins. Bilbo was three generations removed from Balbo and Frodo was four generations removed. So to Bilbo, Frodo was (I believe) a second-cousin, once removed. While Bilbo was a first-cousin to Otho Sackville-Baggins, Frodo was much more distantly related. Bilbo was related to the Brandybucks by marriage only. But his mother was Belladonna Took, daughter of Gerontius (the "Old Took"). So Pippin was a closer relation to Bilbo than Merry was.
As for Frodo, he was related to both the Tooks and the Brandybucks because his grandmother was Mirabella Took and his grandfather was Gorbadoc Brandybuck, both parents of his mother, Primula Brandybuck. Primula married Drogo Baggins. He was also a distant cousin of Fredegar "Fatty" Bolger who helped him set up house at Crickhollow and stayed behind to face the attack of the Ringwraiths. Sam's history is interesting enough but what's even more notable was the number children he sired - thirteen. Among them can be found the names Bilbo, Frodo, Merry, Pippin and Hamfast. While Merry did wed Estella Bolger, it seems he had no children. Pippin, on the other hand, had a son with Diamond of Longcleeve. His name was (not surprisingly) Faramir.
I'm sure that other observations can be made from these records but I'll leave those to other readers. Next, we'll wrap it up with Appendices D, E & F: Calendars, Writing and Spelling and Languages.