Ending (SPOILERS)
I enjoyed this movie much more than expected. The ending wasn't that bad either, but I think it could have been a bit better.
Here a couple of alternate endings that would have worked imo.
1) Happy ending
Same ending, but after the final credits, you see that Bob travels to the past, and falls in love with Bobbi.
2) Sad ending
After he returns to the future, he decides not to go back, because she never really believed him, plus he doesn't want to ruin her marriage. She marries Richard, and they go on honey moon in a cruise on the Pacific Ocean, but the boat drowns and they die -> The boat where they find the book in the beginning (infinite loop)