Why Bnei Yisaschor?
Reb Tzvi Elimelech of Dinov used to feel a more than usual "high" when it came to Chanuka. He knew he wasn't from the family of the Chashmonoim, because he wasn't a Kohen. He decided to travel to the Chozeh of Lublin to inquire about this. As soon as he walked into the room of the Chozeh, the clairvoyant tzadik told him that he descends from the tribe of Yisaschor (Yissachor); the reason he feels such a high on Chanuka is because many of the judges in the court of the Chashmonoim were from the tribe of Yissachor. That's why he named his sefer on the Yomim Tovim, Bnei Yisaschor, and that answers our question why there is such an enormous amount written about Chanuka.
Besides Sefer Bnei Yisaschor, Reb Tzvi Elimelech wrote many seforim on many different subjects; Chumash, Nach, Gemara, Mishnayos, Mitzvos, Kabbalah and more. They are all great works but Bnei Yisaschor is the most famous, quoted heavily by many Litvishe and Sephardishe Rabbonim. This sefer helps you get a feel as to the inner workings of every month of the year. Even for the month of Cheshvan, he gives you an understanding of what the month is about. You can go through the whole year, and instead of each day being "just another day", each day has real meaning, even if it isn't a Yom Tov.
When it comes to a Yom Tov, and you read what he has to say (at least part of it, as there is a huge amount on each Yom Tov) it gives you a whole new feeling and understanding as to what the Yom Tov is about and the reasons for many customs. This sefer really gives flavor to the calendar and he gives reasons why each Yom Tov falls out in a specific month. Bnei Yisaschor is definitely one of those seforim that helps one go through the seasons without doing everything by rote. I feel indebted to this great tzadik for making the Festivals of the year come alive, at least a bit more, for me. This and his other seforim are available in PDF form at HebrewBooks.org.