S. readii

I've got a S. farnhamii / readii which looks almost identical to the one on page 58 of The Savage Garden. Does anyone know which subspecies of rubra might have been crossed with leucophylla?

Judging from the picture in the book on pg 58 I would say the only way (from the distance of the shot) to tell that the plant is in fact even a hybrid.
It looks like a S. leucophylla, so it must be the result of a cross the Author made or one he knows the history of.
Because a plant is crossed doesn't mean it will have much of a "hybrid" look.  In the case of the plant in question it strongly resembles a pure S. leucophylla with good red coloration.
It doesn't show S. rubra much if at all (again the shot is far away).
As S. readii is a natural hybrid, thus the name the natural hybrid would be with wavy hood S. rubra wherryi or S. rubra gulfensis.  The hybrid with rubra wherryi is very common in habitat, and not all that rare in selected sites with rubra gulfensis.  Most of the field locations with rubra gulfensis are on a air force base and acess is not open at this date to the public, nor was it as easy to come across.  The rubra gulfensis plants generally are very easy to tell.
I had to stop marketing a hybrid between N. bicalcarata x ampullaria as the clone I had available did not look like a hybrid at all but just a pure N. ampullaria.  This is common even though it was certainly a cross between both Nepenthes.  I didn't feel it showed hybrid features and wasn't worth selling as such.
Recently I have a crossed S. rubra x purpurea venosa out of the seedlings only a few really show both parents with most showing pure S. rubra rubra features.
Out of the few that show both only a couple are outstanding hybrids of both, and that is where a cultivar should show up from.  Not every hybrid deserves cultivar status, though it is common pratice to name every one now it is a bad mistake
Mike
St. Petersburg Florida