Palliser's book is a great starting point. It's also available (cheaper) as an e-book in Chessbase format. And he did some updates on Chesspublishing + participated in a few discussions on this forum.
But for a free taster you can also check out Joel Benjamins 4 articles at
http://www.jeremysilman.com/chess_opng_shrtcts/archive.html. He recommends mostly the same lines as Palliser, but after 1.d4 Nf6 2.c4 Nc6 3.Nf3 e6 4.g3 Benjamin goes for the Bogo-Indian with 4...Bb4+ while Palliser accepts an open Catalan with 4...d5 5.Bg2 dxc4.
The Tango is a very solid defence in practice; White must be really well-prepared to set Black problems and below IM level most Whites are not. But I've found it hard to win with against master-level players (therefore I've also had an even more dynamic defence available for when I needed to win).
1.d4 Nf6 2.c4 Nc6 3.Nc3 e5 has some of the most fun lines in the Tango, but there are a couple of them I'm worried about. But it's easy to "morph" a Tango repertoire later into a Nimzo-Indian-based one that avoids the 3.Nc3 line. 1.d4 Nf6 2.c4 e6 and now:
- 3.Nf3 Nc6
- 3.g3 d5 (or 3...Bb4+) 4.Nf3 dxc4 5.g3 Nc6
- 3.Nc3 Bb4 4.Qc2 Nc6
- 3.Nc3 Bb4 4.Nf3 Nc6
The only extra work needed is on other 4th moves apart from 4.Qc2 and 4.Nf3 in the Nimzo-Indian, chiefly 4.e3, 4.f3, 4.a3 and 4.Bg5.