Due to the Golden Gate update of MacOS, I lost the ability to directly transfer my ebook to my kindle via USB-C. Looking around I found this app that would allow you to transfer a book via local wifi IP address (no internet connection required). Although I was able to dowload the app without paying upfront, i wasn not allowed to upload any book until i pay either a one year subscription or a lifetime (pro) subscription. I think the developer should allow the customer to atleast upload one book to see if it actually works. Anyway, Im writing this review to confirm that the app actually works as described, so if you believe you will be using this app for a long time, I suggest to just go and get the Pro, instead of paying the annual fee.
Sorry the free limit wasn’t clear before you purchased. Bookify for Mac lets you import and transfer books up to 3 MB each for free; larger files require Pro.