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I found this advertised on DotNet Rocks.
Free ebook downloads from Syncfusion. Only requires registration.
ServiceStack Succinctly
Prism 4 Succinctly
Regular Expressions Succinctly
Imperative to Functional Programming Succinctly
Localization for .NET Succinctly
MATLAB Succinctly
NHibernate Succinctly
PowerShell Succinctly
Android Programming Succinctly
Entity Framework Code First Succinctly
MongoDB Succinctly
R Succinctly
Neural Networks Using C# Succinctly
HDInsight Succinctly
LightSwitch Mobile Business Apps Succinctly
BI Solutions Using SSAS Tabular Model Succinctly
Twitter Bootstrap Succinctly
AngularJS Succinctly
Visual Studio 2013 Succinctly
Windows Phone 8 Development Succinctly
Node.js Succinctly
Direct3D Succinctly
SQL Server Analysis Services Succinctly
Assembly Language Succinctly
ASP.NET Web API Succinctly
Visual Studio Add-Ins Succinctly
Postgres Succinctly
Direct2D Succinctly
Windows Azure SQL Reporting Succinctly
Unit Testing Succinctly
TypeScript Succinctly
WPF Succinctly
iOS Succinctly
Windows Store Apps Succinctly
Data Structures Succinctly Part 2
GIS Succinctly
Data Structures Succinctly Part 1
Objective-C Succinctly
F# Succinctly
Knockout.js Succinctly
C++ Succinctly
ASP.NET MVC 4 Mobile Websites Succinctly
LightSwitch Succinctly
JavaScript Succinctly
HTTP Succinctly
PDF Succinctly
Git Succinctly
jQuery Succinctly
Not sure if its a deal. Syncfusion is offering free ebooks since last couple of years. They publish an ebook every other month. Some of these books are good.