You can find the Brookhaven Beer Fest in Brookhaven Park, right in the heart of the new city of Brookhaven north of Atlanta but still inside the perimeter and part of the Atlanta Metropolitan area. This annual event has run for the past 8 years starting in 2000 (prior to 2017 it was held in a different location) - I first attended in 2016 and volunteered to pour for the event organizers in 2018. My review will reflect both years. The park is only a few blocks from the Brookhaven MARTA station - I would recommend taking the train, especially with alcohol involved.
The event is organized by Spiral Entertainment, which also does Oysterfest in February and Luckyfest in June (St Paddy's Day) at the Park Tavern. The Brookhaven Beer Fest is held in June. I found the organization as a volunteer to be fairly well done - these are nice people trying to create fun adult events with a variety of food, drink and entertainment. For 2018 the event had 150 beers from nearly 50 vendors (this number is mixed between beer, wine and food providers - there was also a Vendor Expo that showcased items that don't fit into the food/drink category). There's also music and a food truck or two.
When I attended in 2016 the crowd was quite thick and a bit rowdy - it was extremely hot and I probably drank too much. For 2018 the scheduling was a bit different with the hours a bit later in the day but still extremely hot - the park setting is also much more spacious so you aren't stepping all over people. As a volunteer I worked the first shift for Left Nut Brewing up in Suwanee - we had four different beers (all in cans) available for a good mix of styles: The Lappland Blonde (Blonde Ale), American Obsession (Pale Ale), The Bridge to Nowhere (IPA and the Mighty Banyan (DIPA) - all are quite good.
In all the crowd was better managed than when I attended in 2016 but I don't believe there were as many beer vendors - it troubles me that it started running out so early. If you're thinking about going make sure you get there early or you may not have the greatest variety available to you (this is a good general-rule for all beer festivals but this one in particular). I hope to attend as a volunteer again in 2019 as I had a great time - always good to meet the distributors and staff that are on hand from each of the regional breweries.
(also posted to Yelp)