A piece in the Sydney Morning Herald all about the history of guidebooks has a few paragraphs about Pausanias:

Guidebooks have undoubtedly been around for millennia - what were the Ten Commandments if not a travellers' guide to Mount Sinai? - with the oldest surviving guidebook written by a peripatetic doctor named Pausanias in about AD 160. Believed born in present-day Turkey, Pausanias travelled extensively around the Mediterranean, through Jerusalem, Jaffa, Cairo, Macedonia and Italy but it was a decade spent in Greece that resulted in Descriptions of Greece.

Written for wealthy and erudite Romans as both travelogue and guidebook, Descriptions of Greece was no 20-countries-in-200-pages handbook. Stretching across 10 volumes, it was as detailed as an instruction manual. It trawled through every moment in Greek history bar toilet stops and contained virtual brick-by-brick descriptions of Peloponnese towns, indulging especially in the sights of Delphi and Olympia.

"To modern readers, it's pretty eye-glazing stuff - reading the Description is like wading through a swamp," says Australian-born author Tony Perrottet, who followed Pausanias' trail in his book Route 66 AD. "There are fascinating gems of information in there but they get lost in the endless digression on mythological themes, and the stultifying and arcane asides on the minutiae of Greek history."

But unlike modern guidebooks, which might have a shelf life of a year or two before rising hotel and admission prices render them obsolete, Descriptions of Greece would continue to serve as a valuable guide for centuries. The Romans travelled with it; German archaeologist Heinrich Schliemann used it in 1876 to uncover the ruins of Mycenae; and Perrottet, who followed it in 2000, thought it more useful than contemporary guidebooks.

"I found Pausanias a revelation. Modern guidebooks tend to take their information about the ancient world third hand, or from other guidebooks, and it has no reality, no human context. It's simply boring. You can actually follow Pausanias step by step through the greatest wonders of Greece - up the steps of the Acropolis, or through the streets of ancient Corinth - an amazing imaginative link back to antiquity."

While Descriptions of Greece has little resemblance to a modern guidebook - its bulk wouldn't get it past the mailbox of a publisher - it bears some similarity to the book that would become the genre's unlikely progenitor.

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Not sure whether Strabo's Geography would be considered a guidebook in the touristy sense ...