TNOTB is a bottom-tier Maiden album, despite it's importance to both Maiden's development and heavy metal in general. Though Bruce was a great addition to the band, Number was the first time Maiden started going for all-out theatrics with their music on a regular basis. Some of these songs are great, while others are not.
I thought "Invaders" was awesome when I was younger, but I can't stand it now. It's just so cheesy. From this track, we basically learn that Bruce is a so-called "operatic" singer and, as we'll see later, he seems to also have an affinity for snarling the word "raping".
"Children of the Damned" is good, but uneventful. Kinda boring to the slower more pensive songs Maiden would do later.
"The Prisoner" is a little bit bland, but the chorus is awesome. The song has no right being 6:00 minutes, though.
"22 Acacia Avenue" is silly, but highly memorable. Some really good vocal melodies from Bruce, except they're ruined by how strained and flat his voice sounds.
"The Number of the Beast" is still great, and a one-of-a-kind song in Maiden's discography. The opening riff and scream are classic.
"Run to the Hills" wouldn't care if I never heard this song again. It's good, but it's overplayed. There's that "RAPING" again.
"Gangland" LOL. Forgettable song. Bruce sounds like he drank a carton of milk before singing the chorus. Special Note: DT's version is the only good one, though James sounds like HE's the one who downed the gallon of milk before singing the rest of that cover album.
"Total Eclipse" is a decent tune, but anything sounds good on the back of "Gangland". Once again, Bruce's vocals are wince inducing.
Finally, there's "Hallowed by Thy Name", the obvious rallying point. In a way, this song, and this song alone, justifies the direction Maiden decided to veer off into with Bruce. And thank God they did, because the next album is great.
Overall, TNOBT is an incredibly mixed bag. Some good songs, some bad songs, and immature performances from Bruce that are both bad and somehow impressive at the same time. It's a short album, but drawn-out songs and a bad run toward the middle-end make it seem MUCH longer than it really is.