Something I found relating to the Belarusian language

https://archive.org/details/Paskievic1.djvu/mode/1up

While searching through the internet I found this book on archive.org. It has another book and audio recordings separately also archived on the website.

I understand without the proper audio or teacher the book is only good for vocabulary and perhaps writing out words as most of it would be unreadable to English readers.

I ask if what this book is spewing is accurate and or useful in any way, or is it outdated or inaccurate?