I came across this the other day and I thought it was really good. Syncfusion, a company that makes UI controls for Winforms, WPF, JavaScript, MVC etc, have released a whole bunch of EBooks under the succinctly banner.

Each book is around 100 pages, hence the succinctly name, and Syncfusion say there are no adverts plugging their products in the books. The books are there as a genuinely useful resource.
There are some really cool books, which I intend to read like :
- Localization for .NET
- Powershell
- Entity Framework Code First
- MongoDB
- Neural Networks in C#
- Twitter Bootstrap
- AngularJS
- Windows Phone 8
- Node.js
- ASP.NET Web API
- Visual Studios Add-Ins
- Unit Testing
- WPF
- TypeScript
And many many more. I am going to be adding lots of these onto my reading list. I love the fact that the books are around 100 pages, which means they allow you to dip into new technologies very easily without having to wade through a huge text book.