There were a couple of books in 1988 which should rather be described as booklets. Those were titled "Friends in need", "The Search for the Great Valley", "Cera's Adventure" and there was yet another book which I presume to be similar in nature (but I can't be sure as I don't own it yet) which had Littlefoot in its title. Those books included screenshots from the movie including a few from outcut scenes, and they were based on the earlier script of the movie in which Littlefoot returned to get his friends AFTER he found the Great Valley. Neither of the book includes the whole story from the beginning to the end, and they are not meant to be a series (with one book being the sequel to the other) either.
The land before time book by Jim Razzi is longer and more elaborate, telling the whole story including several outcut or changed scenes (e.g. Sharptooth's eye, Cera's reaction to the idea of taking Spike along, the Oasis scene, the early discovery of the Great Valley etc.) The book includes very beautiful pictures rather than screenshots.
There are quite a few books which appeared later. One of them tells a very sumarized and version of LBT in verses which are clearly meant for a young audience and another one (I need to check out if that one was English or German) manages to tell the story without a single mention of Sharptooth! That book has Littlefoot's mother injured (they never explicitly say that it was fatal) by a volcanic eruption.
Many of the books which appeared later didn't tell the story of the original movie or any of the sequels but totally independent short stories. Most of them are rather simplistic, but some of them stand out as somewhat more elaborate. In Germany some audio plays were made based on the short stories from that books and I must say that they did an excellent job in elaborating the short stories from the books so much as to make them really good audio plays each of which lasts about 20 minutes (there are six altogether).
There are two very elaborate and I three less elaborate books in Germany telling the story of the the original movie. One of these books is written by Karin J‰ckel and was published along with the movie. It is closer to the plot line of the movie (Littlefoot finds the Great Valley AFTER reuniting with his friends) and is illustrated with screenshots. There are a few short scenes not included in the movie, but I strongly suppose that they were entirely based on the imagination of Mrs. J‰ckel rather than some script. The story is nicely told in that book.
The other book appeared later (in the late 90s I think) and it too does a good job in retelling the movie as an exciting story but doesn't reveal any outcut scenes or anything. Instead of screenshots it is illustrated with paintings on every page and they are very well done. A second book by the same author and illustrator was published. It tells the story of the second and third movie in the same style as the first does with the original movie. Those books were published repeatedly with no changes but different cover images <_<
There also is a version of the two books (telling LBT 1, 2, and 3) in one issue and one altered version of the first book in Din A5 rather than Din A4 format (there are minor changes in the text but many pictures were left out and of course the cover was changed to mislead people into thinking that it was a totally new book).
There are also two books (again one of them was published with two various covers) telling the story of LBT 5 along with a number of kid games (find the way through the labyrinth, find the differences between these two pictures etc.). Sadly the quality of the images in the LBT V books is poor (bat version of Petrie etc.).