An app called Fitnotes, which I've used for years, is a glorified spreadsheet in my opinion.
Also contrary to another poster who insists on not tracking your lifts, I find it essential both for making progress and maintaining interest, its somewhat comparable to levelling an RPG character. At the very least its useful for remembering what you've done recently so you know what to do next.
+1 for fitnotes, probably the best app out there for my needs. Very flexible, gets out of the way, and has some basic analytics like plotting graphs and calculating one rep max values (which I never use). The graphs I find very useful to see if how I'm trending over many months.
I only know it on Android, looking at the iOS App Store it seems like they both hijacked the name from Android, yet that FitNotes 2 is marketed as a clone of the Android app. The other FitNotes in iOS looks totally different in function/UI
Also contrary to another poster who insists on not tracking your lifts, I find it essential both for making progress and maintaining interest, its somewhat comparable to levelling an RPG character. At the very least its useful for remembering what you've done recently so you know what to do next.