I went there most Thursday nights in 1979-80. I got in even though the legal drinking age had just changed back to 21 years old from 19 years old for beer and wine in Illinois.
Many times I'd stop at the Fish Keg, pick up a pound of shrimp, perch or some other totally delicious fresh fried fish, 1/2 order of French fries and go into Frankenstein's, sit down at a table and order a beer with dinner. YUMMY!
They had a nice sized dance floor, a couple of pinball games, and good music.
Visit the souvenir shop.