Following are the Books which I refer and Tools which I use to create my Tutorials.
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Books on Excel

John Walkenbach‘s Excel Bible is the best recommended Excel book for beginners as well as intermediate Excel users. A complete guide covering every essentials aspects of Excel.

Written by Greg Harvey, who has sold more than 4.5 million copies of his previous books combined. A great guide on Excel which offers everything you need to get started.
Books on Power Query, Power BI and Power Pivot

Super Charge Power BI written by Matt Allington clearly explains the necessary concepts while at the same time giving hands-on practice to engage the reader and help new knowledge stick.