Calibre is a professional eBook management application. You can effectively organize your eBooks so that you can find the required books with ease. You can convert eBooks to a wide range of formats. Moreover, you can also sync the database of eBooks across eBook readers and smart devices. Kovid Goyal developed this free software in October 2006. It’s one of the most popular eBook management applications, compatible with almost every version of Windows OS. It’s an open source solution that you can download for free. It’s a lightweight application that doesn’t slow down the speed of your PC.