For anyone familiar with memory techniques, there are the old favourites, such as:
Number shape system
Number rhyme system
The Roman Room
There are also some that are new to me, like the Body system,(where you associate up to ten items with parts of the body) and the Dominic System, which replaces numbers with letters which form the initials of famous people.
Mind Maps(devised by Tony Buzan), are also touched on.
As other reviewers have stated, some of the techniques are simply rehashes of others; but I can understand why in a series which needs 52 of them! I haven't seen the Major System mentioned, but the Dominic Technique, devised by the author, is very similar.
Some of the methods just seem plain daft, eg the Remembering Directions technique, in which you have to remember a fictitious journey in your head whilst associating it with the directions given you, perhaps hurriedly, by a local.
Books of this type, regrettably, don't tell you how to remember the everyday concerns regarding memory. Such as buying an anniversary card before it's too late, or where you put your keys. And avoiding the embarrassment of telling someone something you've already told them. Much more useful than remembering a pack of cards!
Oh, and avoiding the embarrassment of telling someone something you've already told them.