Well, as far as I know, the only solution is don't try to use Google books !
It's apparently nothing to do with Sony, but Google, who have decided, it would seem, that if you can't use their app you're not worth bothering with - and the T1 fits in this category.... whether it's all readers I don't know.
So blame Google, not Sony this time ....
Although it seems a bit unlikely that Google didn't give Sony some warning it was going to happen, and that a feature designed into the T1 (the Googlebooks button) would soon be useless.
Which rather makes one wonder why, if they did know, owners of the T1 haven't /weren't told that a feature was going from their reader. Instead of simply pushing people onto their own store. Might have got a bit of sympathetic publicity ?
But look, it's only a shop, when all's said and done - there's a mass of resources and sources legally out there, easily available, for free, and paid for stuff.
And I believe you can access it from your PC.computer anyway. But don't quote me, I've never felt the need to try it.