There is a short free ebook on LINQ that you must absolutely go through. It is called "LINQ Succinctly". The book is well written by Jason Roberts.

You can download the ebook for free from the Syncfusion site: https://www.syncfusion.com/resources/techportal/ebooks/linq

The book has 114 pages and contains many samples. You will go through it quickly and it is really Worth it!