Why do programmers hate SQL

12 Free Books Every IT Talent Should Read

Technical literature for programmers no longer has to cost a lot of money these days. There are OpenBooks for all common programming languages, which are available free of charge in the form of websites or e-books. The abundance of tutorials and online courses is also enormous. We have put together a selection.

Basics of computer science

IT manual for IT specialists

A reading that briefly introduces a variety of information technology topics and gives an overview.
This book is particularly recommended for IT talents who are thinking of deciding to study computer science or an apprenticeship. Here you will find an overview of topics that you will encounter in much more detail in your training.
An online version of the book is available free of charge as an OpenBook:
http://openbook.rheinwerk-verlag.de/it_handbuch/

Object-oriented programming

Object Oriented Programming - The Comprehensive Handbook

Object-oriented programming is arguably one of the most important paradigms in recent years. The triumphant advance of Java is based to a large extent on the spread of object-oriented programming. This book, available online for free, brings you closer to all the important approaches of OOP and lets you immerse yourself completely in the subject.
http://openbook.rheinwerk-verlag.de/oop/

Shell and Terminal

Shell programming

Some hate them, others love them. The fact is, however, that sooner or later every IT person has to deal with what is probably the most powerful tool in modern operating systems. You can find out what options the Shell offers you and what makes your work easier with shell programming in this online work, which is available free of charge.
http://openbook.rheinwerk-verlag.de/shell_programmierung/

Databases

SQL tutorial

This detailed tutorial is available online and even offline as a .pdf download and offers you much more than an introduction to SQL. From simple queries to extensive database structures with (foreign) keys, you are offered a lot of background information.
http://www.tutorialspoint.com/sql/sql_tutorial.pdf

The following online tutorial is also helpful:
http://www.guru99.com/sql.html

Programming languages

C from A to Z

The book "C from A to Z" is also available free of charge in an online version from the Rheinwerk-Verlag as an OpenBook.
This work on the programming language C is suitable for beginners who have already had contact with an imperative (or even procedural) programming language, as well as for advanced programmers. Especially as a reference work, it covers the entire scope of the C programming language.
http://openbook.rheinwerk-verlag.de/c_von_a_bis_z/

Visual Basic

An exciting and comprehensive book about Visual Basic. Particularly suitable for beginners, as almost all topics are explained with step-by-step instructions so that what you have learned can be directly applied in practice.
http://openbook.rheinwerk-verlag.de/einstieg_vb_2012/

Java is an island too

Probably the classic among the OpenBook publications is the extensive work "Java is also an island". On over 1300 pages you can get to know Java from the ground up through to special use cases.
To work through this book, however, you should take several weeks / months alone due to the wealth of the content. The learning success is certain, however.
http://openbook.rheinwerk-verlag.de/javainsel/

Web development

HTML5 manual

Web development can no longer be imagined without HTML5. The HTML5 manual guides you from the simple creation of static HTML pages to complex layouts and rich media content. This book in the form of a website is also ideal as a reference work for building HTML5-compliant websites.
http://webkompetenz.wikidot.com/docs:html- Handbuch

Virtualization

VMWare - virtual servers in professional use

The trend in the professional environment is moving more and more towards flexible and powerful solutions in server virtualization. The work "VMWare - Virtual Server in Professional Use", made available free of charge as OpenBook, offers more than just an introduction to the subject. After working through it, it enables you to design and implement professional virtualization projects.
http://openbook.rheinwerk-verlag.de/vmware/

Operating systems

Debian GNU / Linux User Guide

The Debian GNU / Linux user manual is also readable online and free of charge. If you work with Debian, you will find the perfect documentation of the operating system and its possibilities here. Due to its proximity to other Linux distributions, this work is not only interesting for Debian users, but also offers valuable input for users of other Linux operating systems or system administrators.
http://debiananwenderhandbuch.de/

Linux - The Comprehensive Guide

Already a bit older (current edition from 2012), but still great in many areas in terms of documentation. The book conveys basic knowledge of Linux operating systems and is good both for an easy introduction, but also conveys extensive practices and knowledge about the system administration of Linux systems and is devoted to system security with great dedication. If you want to keep it up to date, you can use the printed version of the book in the current edition from the end of 2015.
http://openbook.rheinwerk-verlag.de/linux/

Windows 10 for IT professionals

There are also up-to-date and free books for the Windows group that provide comprehensive knowledge about the current Windows 10.
The manual "Windows 10 for IT-Professionals" can be downloaded free of charge directly from Microfot.
The work first gives a basic overview of Windows 10 and then provides in-depth information on more specific topics such as security and privacy in further chapters.
https://blogs.msdn.microsoft.com/microsoft_press/2016/02/08/free-ebook-introducing-windows-10-for-it-professionals-technical-overview/

Other Recommendations

In general, the OpenBook series from Rheinwerk Verlag can generally be recommended: https://www.rheinwerk-verlag.de/openbook/

If you want to dive deeper into the subject, or just like to read books in paper form, it is of course still recommended to borrow books from the local library or to buy specialist literature.