7-Card Stud: 42 Lessons How to Win at Medium & Lower Limits by Roy West is regarded as one of the best 7-card stud books written. Although just over 200 pages, it presents a variety of important strategies for playing 7-card stud.
Aside from this text the only literature on 7-card stud that is probably even worth looking at are the book by 2 + 2 by Ray Zee and the chapter in Super System 2, however this is by far the best text. Because 7-card stud is a game where you can see many more cards than in hold'em or omaha, and it's also usually played in limit format, you can often use more concrete rules regarding how to bet and how to interpret bets. In games where you can see more cards and the betting is limited, the game is much more mathematical in nature and doesn't require as much work adjusting to your opponents or reading their hands.
The lessons presented within give you a step by step guide to playing each street and each type of hand, such as trips, a flush, or various draws. It also discusses starting hand requirements, which are very important in stud. Positional playing isn't as emphasized in stud since the best hand showing always bets first, but this is discussed as well.
This book is an absolute must have and should be a regular read for any player who plays 7-card stud at any level, online or offline.