As you might expect, the 24 players were already listed on the 'Index of Players'. For GMs Hammer and Rapport, it was only their second appearance in a World Championship event, and for GM Riazantsev it was his third.
My page on the 2017 Grand Prix shows that GMs Mamedyarov and Grischuk qualified into the forthcoming 2018 Candidates Tournament (congratulations to both!), while the chart on this post shows how close was the race in terms of points scored.
The 2017 GP, the fourth such series of events to be authorized by FIDE, was the first to start after the previous cycle had finished and the first to take place in a single calendar year. For the wrapup post on the Grand Prix for the previous cycle, see 2014-15 GP (June 2015).