It wasn't too long after EPCOT Center opened that their guide books changed format from a small, nearly square shaped booklet with a spinning wheel inside to the taller brochure style format we are used to today. I acquired my first of this new style guide during a family visit to Disney World in late March, 1984. This guide book is dated 1983, but the inclusion of Horizons (it was listed as "opening Fall 1983" on the guide we picked up during our 1983 Disney World trip), which opened on October 1, 1983, means this guide was from our my second trip that included a visit to EPCOT Center, in 1984.
The guide book was very similar in structure to the Magic Kingdom guides of that era, with a foldout map inside the front cover, and detailed descriptions of the attractions, shopping, and dining found in each Future World and World Showcase pavilion. Horizons is the only new pavilion added from the 1982/early 1983 map, though the "future site of The Living Seas" and "future site of Morocco" now appear on this park map. Norway wouldn't appear as a coming attraction on maps for a few more years.
The map also shows a long forgotten forerunner to the various food festival booths that would later line World Showcase Lagoon, a small seasonal spot known as the Renaissance Food Festival. I don't remember ever visiting this place, but at least there's some evidence that it actually existed thanks to Michael Crawford's Progress City, U.S.A. website.
The rest of the guide looks like most Disney guides from that time, with photo tips, recreation and other Disney World resort information, a property map, and ads for Disney films coming soon to theaters near you.