Pete, Ive got a few, some big on word content, some on photos. I havent as yet found a book dedicated to the 'new' gtv/spider. Im pretty sure there isnt one, Im always looking.
Anyway if you want a book that covers all the models with not too much writing and plenty of pics, try 'alfa romeo sporting saloons' - john tipler. Unfortunately all pics in b&w but excellent none the same. Another one with really nice pics but not as many is 'alfa romeo colour family album' by andrea and david sparrow. All colour and a few of spiders and gtvs. Sad name for a book though. Bet they do the alfa picnic scene.
Alternatively, try amazon but its hit and miss with the books on there.
i got the Alfa Romeo (always with Passion)
by david owen, published by 'haynes', and it covers the entire history, but was disappointed to find although it does mention the 155, there are no pictires (sacreligem i think)..