Unfortunately Lamport's LaTeX book (and many other LaTeX related books) are often too elaborate, or you simply can't find what you are looking for because it's not in the index. Finding documentation can also be hard if the index has 5 or more entries to the subject, as is often the case in the TeX book.
A more convenient way to get help on LaTeX related items is a MS-Windows hypertext help system that can be started from the 4TeX utilities menu. The help file describes LaTeX 2e, not LaTeX 2.09. The help was adapted from the old LaTeX 2.09 help file by T. Martinsen.