Land Books go hand in hand with Upper Canada Land Petitions (UCLP). In effect, the results of the petition were recorded in the Land Books. Thus, if you have the petition(s), from UCLP, then there will be next to nothing in the Land Books for that petition. Sometimes there is, but that is rare.
You don't usually find a Land Book reference except in the index to Petitons (UCLP index)
The only time I've found the land books to be quite worthwhile is when a petition has not survived. Then you can at least find out if your ancestor was awarded land by referring to the Land Books.
Read more about land in Upper Canada (Ontario) and granting or selling of it