The main reference for stress and strain formulas
This is one of the best book "sui generis": it's only (but not only...) a complete review of formulas for stress and strain. You don't need this book if you are looking for a book about stress and strain... you will find here only formulas with some brief explanation but anything more... Someone then may ask: why I should buy this book? It's useful to get an idea of what you are doing when you are using more sophisticate tools. I use this book for the following purposes: (1) to model component behaving in computer aided simulations and (2) to check and review FEM analysis results.
Very good book, but maybe you don't need it on you desk.

Roark's
I like having a Roark's around. It is handy for stress and strain problems.

Junior does not have the quality that senior had.
While this volume is about 30% larger than my 5th edition, it has some glaring errors. When you get pointed to a table, you will not find tables with that number. The tables are titled but not numbered according to the referring item. Major PITB trying to figure out if the table that I found was the correct one.

Five Stars With no Doubt.
During my years as Structural Calculyst this book was always on my right side on my desk, and when I needed it, it was ready to help me find my way. One really very good Engineer has never found all formulas in his head, instead he should be able of finding them out on good references and really know how to use
them all. This is the best reference book you are going to find when formulas is your subject, just buy it!
The only book I know better than this one is written in German and few people are able to read in German, so!

very useful handbook
Very helpful book in engineering job, but unfortunately I've found some mistake (the reason for 4 stars).

In general you can find lot of formulas in this book. This book is also very well known and that's the reason for recommending it. You can just refer to Roark's formulas and everybody knows what's that.