Well, it depends. If you want something more fun, Beautiful Freak is there, but I personally find it a bit dated and inconsistent. The hands-down consensus favorite is Electro-Shock Blues, but every song is about sickness and death and grief so it probably would not be the easiest listen. It is, however, his most vital creatively. There are plenty of great songs, but I want to highlight this underrated track:
Eels - My Descent Into Madness - YouTube
A dark horse but equally recommendable album is Daisies of the Galaxy, which is a corker and stretches the Eels sound while remaining quite fun. There are great ballads too, particularly this one:
The Eels - It's a Motherfucker - YouTube
Blinking Lights is fucking
long, which may be a major turnoff, though I personally enjoy it a great deal. Trouble With Dreams is remarkable and, unsurprisingly, one of the best tracks, but there is more than enough good material to go around. I wouldn't recommend the album as an introduction, but if you enjoy any of the albums I mentioned prior to this, you need to hear it. Everything after Blinking Lights is unremarkable and derivative of his earlier work, albeit duller.