When I worked in England, I was fortunate enough to have reason to be in London fairly frequently. Whenever I was down there I'd try to spend some time browsing the bookshops on the Charing Cross Road. Every now and again I'd stumble across something really interesting. One day I found these: one of the most exciting finds ever. Better than the 3D Geometry perhaps or the facsimile copy of Tschichold's die neue typographie (yet to be bloggged). I bought all six editions being sold: 4 new series, 2 old series at the absolute bargain price of £1.50 each!