Coming soon:

Arsène Lupin Intervenes
The Memoirs of Arsène Lupin
Arène Lupin Returns
Arsène Lupin versus Sherlock Holmes (aka Arsène Lupin versus Herlock Sholmes)
813
The Confessions of Arsène Lupin
The Crystal Stopper
The Golden Triangle
The Secret of Sarek
The Teeth of the Tiger
Eight Strokes of the Clock
Arsène Lupin, Super Sleuth
The Melamare Mystery
The Girl with Two Smiles
Arsène Lupin (book of the play)
Arsène Lupin (English translation of the play)

Also, I will be putting up a PDF file of all of the books in the original French.