I just finished reading Ending Day by Day. This is the fourth and fifth books in the Full Metal Panic light novel series which the three anime series were based on, specifically, the second Kyoto Animation series, The Second Raid.
It's a little interesting seeing what they pulled out of the book and what they added for the TV series - a little flashback during the Gauron scene got expanded into a major filler arc (if that isn't total jibberish) during the original Gonzo series, Gauron's pocket dragons got turned into women for the killer-moe factor, and an entire mini-arc complete with additional missions and underground firefights were inserted into the middle of the story to fill out the anime version of The Second Raid. The books flow more organically and make a more perfect whole, but I can see how a TV series can't back-load the majority of the fight scenes in the last five-ten minutes of the production. You could say that the structure of light novels lends itself to one big fight every two hundred pages, whereas a TV series better have some action every two to three episodes before the sponsors and the fans go postal.
We were lucky to get these two volumes in North American publication at all, as the series was canceled by TokyoPop the other year, and then tenatively revived. Light novels don't sell for peanuts in the American market - they're too fanboy and short for the mass paperback market, and too wordy and ancillary for the otaku market. But I do know that I'm eager for the next book in the series. We didn't get anything more from the animation studios, and word is that at least one reason is that the novels go off on a somewhat grim and gloomy tangent which could alienate the anime audience.
Nevertheless, I want to read Dancing Very Merry Christmas, as Japlish and goofy a title as that may be. Hold it together, TokyoPop! Keep on publishing!