I used to be a very fast reader, roughly like your wife. However, I suffered a brain and vision injury. I applied some old techniques that I knew from high school (I attended a speed reading course) and some new ones (which address the short term memory issue). One thing that had been mentioned in the course is that a lot of slow readers 'read out loud' in their head. This really slows them down. However, you could also have some kind of learning disability that I know nothing about.
Here is my suggestion. Get an audiobook and etext of the same book. Follow along. Use an audiobook app, if possible. Most audiobook apps have the option to have the reader read faster. I would increase the speed and continue to follow along. You are going too fast if you are not enjoying the reading or losing the thread of the story.
Why would this help? You use a different part of the brain when you read vs. when you listen. Sometimes, by both listening and reading, you can 'fix' the reading part, at least to a point. This is how I progressed. This may not eliminate the problem at all, though, if the plot or the writing is quite complex. I have actually found fantasy novels harder to read than science fiction. Not sure why.
Hope this helps. I know it can be frustrating. I lost 10 years of reading because of my issues, so even if all you can read is one book a month, that's more than a lot of people read.
