Generally, whichever became a movie, it was at least purchased first, gets the rights to the character AFAIK. It was a big deal with the character of Ray Nicolette, played by Michael Keaton, a fairly major character in Elmore Leonard's Rum Punch and a minor character in Out of Sight.

Rum Punch became Jackie Brown the year before Out of Sight became a movie, and Miramax was originally not going to let the Nicolette cameo happen in OoS, until Tarantino stepped in and convinced them to let Soderberg use the character and even have Keaton play him again.

Chasing Amy was always his best reviewed movie in the 90's. It's generally credited with saving his career after Mallrats bombed. (Mallrats later became a big hit on home video, but it did about two million on a six million dollar budget at the box office. It also got mostly negative reviews. Amy on the other hand got mostly raves and made $12 million on a $250,000 budget.)

Amy has pretty much always been considered his best film, though it's often viewed as problematic.

It is odd that the movie that is almost universally considered the worst was also the most successful of the original five. I guess it just hit that 3D craze at the right time.