How to combine imported audiobook tracks and add to iBooks?

I am trying to add an audio book I bought to iBooks. I have already imported the tracks from all five CD's. Under the "Get Info" option, I added artwork to each file, checked the box for "compilation", under genre I selected "spoken & audio", and selected "remember playback position under options. However, it still shows five separate files for each CD I imported. Is there a way to combine all five into one continuous file? Finally, how do I move the file to iBooks so that I can steam from all my Apple devices?

I use an iMac Retina 5K27inch. Model year 2017. Processor is 4.2 GHz Quad-Core IntelCore i7. Graphics is a Radeon Pro 580 8 GB. Memory 64 GB 2400 MHz DDR4. macOS Ventura 13.7.8