We are also designers and we wanted to help design teams in daily work. So we started with notepads and now we're providing complete tool for creating products and services in cooperation with other members of design team and clients.
With UXPin you could prepare wireframes, create prototypes and add comment on pixel perfect projects. And everyday we try to add something what make your work easier/better/more functional.
A very basic introduction that describes some core concepts that rely on human perception. You'll find it useful e.g. when you're a developer that wants to have a little bit more understanding of the front-end part or when you're at the very beginning of your web design adventure. Short and reads easily, though a bit like a student assignment.
Unfortunately, even though the ideas are still quite valid, it doesn't survive the test of time because most of the external links don't work anymore. IMO if you go through the trouble of preparing a nice PDF book it's better to contain all the information within it - like with some of the examples.