what is epub extension?

"EPUB is an e-book file format with the extension .epub that can be downloaded and read on devices like smartphones, tablets, computers, or e-readers. It is a technical standard published by the International Digital Publishing Forum (IDPF). The term is short for electronic publication and is sometimes styled ePub" https://en.wikipedia.org/wiki/EPUB. 

Here some software to open epub;
1. Epub File Reader, it is free software it is nice and easy to use. 
    u can download at http://www.epubfilereader.com/

2. Sumatra PDF is a free and open-source document viewer, it supports many      document formats including: Portable Document Format (PDF), Microsoft            Compiled.HTML. Help (CHM), DjVu, EPUB, FictionBook (FB2), MOBI, PRC, Open XML Paper Specification (OpenXPS, OXPS, XPS), Comic Book Archive file (CB7, CBR, CBT, CBZ).It is developed exclusively for Microsoft Windows, but it can run under Linux with help of WINE. download the sumatra pdf here

The Illustrated Encyclopedia of Weaponry by Chuck Wills.

This book explains the history of weapons from time to time, with illustrations accompanied by clear descriptions we are invited to wade through time to get to know various weapons. What, why guns are created, over time and knowledge of weapons are changing.

"Weapons have a unique appeal for collectors and museums because of their technology, materials, craftsmanship, and beauty. The most ordinary weapons tell the story of the time and the society in which they were made and used. Though they served and continue to serve deadly purposes, weapons allow a glimpse into human history" ROBERT LINDLEY

Creating Characters with personality by Tom Bancroft

"Creating Characters has never been easy for me. The designs don't gives themselves up without a struggle; there are no formulas for a quick and easy path. To design the character i do hundreds of drawing, exploring and waiting for that moment of recognition when i can see the face of the character I am searching for staring back at me. That is the magic moment I am always working to achieve" Glen Keane