I was working on my project yesterday. Closed project. Now today suddenly, went to start up scrivener and nothing. The rainbow wheel spins & spins and nothing. I cannot access any of my projects.
What do I do?
I don’t even know what might have happened to cause this because I did nothing unusual yesterday.
Help. 
Ok, so now I think it’s just that my last file was corrupted. That is huge problem because it’s a huge book over 350 pages! What do I do now if I can’t access the file with all my work?
Ok. I figured it out. My last file must have gotten corrupted. Perhaps because I left it open while my son played mineplex. Which should not effect my scrivener file, but I believe that’s the culprit.
At any rate, I opened scrivener, went to preferences, backups - then opened back up file (button shown on window), and opened my last backup. Thankfully it worked. I manually backed that up, saved as new project also. Some changes are lost, as I said because my setting was to only backup on project close - but what ever - at least all my hard fluffin’ work isn’t gone.
Yikes. 
Ok, so now I was compiling my scrivener manuscript as a paperback with parts and it crashed and corrupted my file. Word of warning - back up a copy of your writing BEFORE you compile. Something about the compiling process seems wonky! 
It could have been any number of things, there are a lot of factors that can fall under the umbrella of corruption, and the vast majority of them can be fixed, usually with no loss of settings or data. For example the compile settings file might have been damaged by the crash, that’s unlikely but if happened in the instant the file was open to update your settings, it is possible (plus the Mac preference writing is known to be flaky, which is why you often see troubleshooting step #1 as resetting preferences on Mac software help pages across the ’net).
A tip: in the Backup preferences you can switch on the ability to create a backup when pressing Cmd-S. I love this option as it allows me to fire off a backup whenever I feel like I’ve done enough work to merit doing so. I also increase the number of stored backups to 25 so that I don’t have to worry about making several backups on a busy day without the system deleting yesterday’s and earlier.
Do you still have the copy of the project that won’t open? You mentioned it contains edits not found in the backup you restored from, if it’s worth the trouble to try and get it working, we could try taking a look at it or helping you do so (opening a personal ticket with tech support would be best for that.
Finally, if the compiler is still crashing on this project, let me know. That’s usually one of three problems: 1) the project is massive and the converter is running out of memory, trying RTF can often help, (2) there is a corrupt image file somewhere in the text, the compiler has to process them and if it can’t open and save the image that will crash the compiler, and (3) similarly, a bad Unicode character, such as NULL, can mess up text processors. You can track down the latter two problems by selectively compiling bits at a time until it crashes, then narrowing it down from there until you have culprit file.