Let's get this out of the way right off the bat - the sound quality on this release isn't the best. The show was picked for historical purposes (it appears to be one of the earliest existing recordings of the band with Flo and Eddie as the front men) rather than due to outstanding performances or great sound quality. It sounds about on par with some of the better entries in the Beat the Boots series. So if so-so audio quality is a deal breaker for you, you might want to skip this one. That said, the album is perfectly listenable, especially if you're used to listening to bootlegs.
The CDs are sourced from soundboard recordings (I'm guessing). The first half or so of the first show was unfortunately recorded over tape that already had music on it, and there's some bleed-through during the quite bits. It reminds me of shows I've been to where the P.A. system is picking up a faint radio signal, so you occasionally hear other music behind the live performance. In order to alleviate the worst spots, Joe Travers decided to copy the right channel over the left, so for most of CD 1 the sound noticeably shifts back and forth between stereo and mono. Personally I would have preferred if he'd just left it in stereo, but maybe the bleed-through problem in the left channel was really so bad that he had no choice.
There's what sounds like a bad edit early on disc one - after some sound checking and Zappa telling the house sound man to start the tape recorder, the band launches into King Kong. But after just a few minutes of what's normally a long song, the music cuts to the beginning of Wonderful Wino, which sounds like it's faded in slightly. Just a really weird edit all around.
Since this show is from early in the Flo and Eddie era, the band probably didn't have much new material worked up yet, so the set list leans heavily on songs made famous (well, amongst Zappa fans) by the original Mothers of Invention. The album comes from two shows, so there's also some repeated songs - two each of King Kong, Call Any Vegetable, and Sharleena, but there's a lot of improv and jamming in there, so the duplication isn't too bad.
In case you're wondering about some of the unfamiliar song titles - Agon is just a very brief Stravinsky quote. The "Mondello" tracks are spoken bits inspired by the fact that multiple people mistook Flo and/or Eddie for the actor who played Larry Mondello on "Leave it to Beaver" (the "23rd" part was due to it being the 23rd show of their tour). Justine is a quick and dirty cover of an early rock and roll song co-authored by Don "Sugarcane" Harris, who worked with Zappa. "A Piece of Contemporary Music" is an improv/freak out that Frank introduces by saying that it's a woodwind piece that the band was practicing earlier in the day, and "some of these guys know how to play woodwinds, and some don't. Guess who's who."
When all's said and done, is this really a must-buy for Zappa fans? Well, it's a fun album (especially disc 2) and it does document a rarely-heard era of Zappa's live performances. If you're a huge Flo and Eddie fan (or the rest of the band - Ian Underwood, George Duke, Jeff Simmons and Aynsley Dunbar), you might want to pick it up. If you want to hear a different spin on classic Mothers material, you could give this a try. But the audio problems and the fact that most of this material already exists with better sound quality and (arguably) better performances on other albums cause me to warn casual or beginner Zappa fans away from this one.