Hey Dimery, you forgot a hard rock album for your book! I'm being sincere! I'm not entirely sure I would call Dreamboat Annie essential per se, but the Wilson sisters et al. prove that they rock harder than most of the "classic rock" chumps on the main list.
I haven't listened to Dreamboat Annie in a long time, but it's a lot poppier than I remember. Despite being a hard rock album there's hooks all the way through the tracklist so I think that will give it a wider appeal than other bands in the genre. To borrow software terminology, I think you could call this "firm rock", the hooks make it accessible and an easy listen but the harder rocking aspect gives it a much needed oomph.
The star of the show is easily Nancy Wilson. Her plucked acoustic guitar playing gives the songs a soft and folksy feel to most of the songs, which helps to emulsify the pop with the harder elements. She also is proficient technically while still managing to to transform the fiddlier elements of the guitar into the aforementioned hooks, the intro for Crazy On You is a perfect example of that. I've never considered Nancy Wilson one of the "greats" in the guitar world, but this album is making me reconsider that. I will have to check out more Heart albums, because her performance on here is nothing short of spectacular.
That's not to discredit the other members! Ann Wilson has wonderfully powerful vocals that works superbly with the more passionate songs, again looking towards Crazy On You where she arguably steals the show from Nancy from the choruses onwards. The lead electric guitarist (who I believe is Robert Fisher) also plays a great part on some of the harder rocking songs.
There's a few other pretty important elements that act as the secret sauce as to why this album is so good. There's a lot of folk rock and soft rock elements, which as stated before acts as a pretty good counterbalance to the hard rock. There's also a little bit of prog in here, giving the album much needed complexity. I think a good comparison is Led Zeppelin IV, which I'm guessing was a major inspiration.
This album is also home to possibly my favourite song of the boomer hard rock era that I alluded to earlier. That song is Crazy On You. After a phenomenal guitar intro from Nancy, she effortlessly transitions into the song's main motif, swiftly followed into the song proper which is another hard rocker. This combines /every/ positive element I described about the song succinctly into a 5 minute runtime. I don't think I'm exaggerating either, this should be considered a classic among the likes of Gimme Shelter and Bohemian Rhapsody, and if you haven't listened to it before do so now!
I see a lot of other reviewers criticise the second half for being much weaker than the first, an opinion that I don't really agree with. Sure there's a drop in quality, but even the best bands aren't going to be pumping out songs at the quality of Crazy On You left and right. There's I'll Be Your Song which is a nice ballad, and Sing Child which is probably the hardest song on the album. I wouldn't really change anything about it other than the title track reprise at the end which was kind of unnecessary.
Should it be on the main list: Yes. They're one of the original female led rock bands, and quite frankly it's more interesting than most "classic rock" albums that were in the books.
Top 3 songs: Crazy On You, Dreamboat Annie, Sing Child