In the book "Drupal 7 Webform Cookbook" author Vernon Denny takes us on a journey through the various aspects concerning the popular Webform Drupal module. Readers of this book are shown step by step how to leverage the power of this module, and associated other contributed modules that extend its functionality, to create everything from simple contact forms to complex, multipage and conditional forms.
The book is written in the cookbook format, where each chapter contains a number of 'recipes' that users could pick out to perform a specific task they had in mind. I have the feeling that the book is somewhat forced inside this format, and doesn't suit it very well. Much of the recipes depend upon knowledge that was explained earlier, or configuration that was performed in earlier recipes. So I think readers will get the most of it by reading the book in a linear way anyway, and just skipping sections they might already be familiar with.
This minor criticism aside, the book covers an extensive range of topics related to webforms, that will surely help you get the most out of its functionality if you previously only created some simple forms with the module.
Lots of time is spent on form components: starting with a detailed overview of the default components that Webform comes with, over contributed modules providing extra functionality, such as the "Select (or Other)" module and "Options Element" module, up to writing your own custom Webform components.
I was also pleased to see that the topic of form validation got quite some attention, by covering the basic functionality provided by Webform itself, as well as the Webform Validation (a module written by yours truly) and Clientside Validation modules. With the help of useful examples, the author gives a clear overview of the possibilities that are available in the area of form validation.
Furthermore the book also covers other important topics in great details, such as working with and evaluating form submissions, importing & exporting submission data and writing custom modules to implement specific needs you might have for your form(s).
This book is primarily targeted towards site builders, not necessarily Drupal developers, so the required programming skills to understand what's going on are pretty limited. Readers without PHP knowledge should get pretty far in achieving their goals without writing any PHP, with the help of this book.
Overall a nicely written and detailed walk through the Drupal Webform universe, that should help you achieve more than you thought was possible with Webform after a first glance.