I really feel like I've got to see some of the screen adaptations now, to further my education if nothing else.

I can recommend Topper (1937) and I Married a Witch (1942), although technically the latter novel was only three-quarters complete at the time of author existence failure and obviously I have no idea how closely either film relates to their book. I have zero faith that Turnabout (1940) is in any way good, but have nonetheless wanted to see it ever since finding out someone even tried in the era of the Production Code to make a body/genderswap film with mpreg.