If you want to understand the book of Isaiah, read Understanding Isaiah by Donald W. Parry, Jay A. Parry, and Tina M. Peterson. No joke, within 15 of reading the book, your understanding will have been completely transformed. (Can I use the word ‘understand’ any more in 2 sentences?! Hopefully you catch my drift.)
And I’m not even going to reference another book at the moment, because this is the ONE you need.