Kamisama no Memochou
Kamisama no Memochou (God's Notebook)
Written by Hikaru Sugii
Illustrated by Mel Kishida
Published by Dengeki Bunko
Alice is a hikikomori, but just because she never steps outside her apartment doesn't mean she can't be a detective. With her cell phone and computer, she directs an army of minions across the city to solve mysteries.
This one is off the beathen path -- not only is it a mystery, it's dark and gritty in tone despite the moe girl on the cover. There aren't a lot of other series like it -- there's a bit of Durarara in the plot, but more realistic; a bit of Zeroth Maria in the atmosphere, but without the supernatural; a bit of Book Girl in the tragedy porn, but more hard edged about it.
There was an anime many years ago (released in the US as Heaven's Memo Pad), but it was lackluster thanks to the dumb decision to mix up the order of the stories, so the books would have to sell on the basis of plot and the cover ... but look at that cover!