For an in-depth history of Poland, I would highly recommend God's Playground: A History of Poland by Norman Davies. It comes in two volumes, "Origins to 1795" and "1795 to the Present". I own both but you can buy them separately depending on which parts of Polish history you are interested in. It's certainly the gold standard for English-language books on the subject, but I found it written in an easy to read and logical manner, especially since I'm not a native English speaker!
I personally like "Origins to 1795" because I am a huge history buff for medieval history, and Poland has one of the most interesting and multifaceted medieval histories of Europe. During the 1300s it was the only major kingdom to escape the horrors of the Black Plague and actively protected its Jewish population while they were persecuted almost everywhere else.
If literature is your cup of tea, I would highly recommend looking into Poland's national writer Henryk Sienkiewicz, you may have heard of some of his great books Quo Vadis, The Teutonic Knights, On the Field of Glory, In Desert and Wilderness. Sienkiewicz also traveled extensively in the United States, and lived in Anaheim, California during the 1870s.
Podcasts are also a great way to digest history, this one is excellent albeit very in-depth https://www.historyofpolandpodcast.com/episodes
YouTube Videos are also great resources, here is a nice animated series of Polish history, I really liked:
Part 1 - https://www.youtube.com/watch?v=jV98XaAlg1o&list=RDCMUCQD-0MjUbDBwm2UTVYr0Dag&start_radio=1&t=0
Part 2 - https://www.youtube.com/watch?v=8CwFHH_y2So&list=RDCMUCQD-0MjUbDBwm2UTVYr0Dag&index=2
For a fun blend of unique history and travel destinations in Poland (similar to Atlas Obscura): Polish Highways & Byways: Tourist Atlas
Hope this helps pass the time, especially these days :)