In the lead-up to the album's release, a series of teaser advertisements depicting each symbol was placed in the music press. The album was a massive instant seller. It entered the UK chart at No. 10, rising to No.1 the following week and stayed on the chart for 90 weeks. In the US it stayed on the charts longer than any other Led Zeppelin album and became the biggest selling album in the US not to top the charts (peaking at #2). "Ultimately," writes Lewis, "the fourth Zeppelin album would be the most durable seller in their catalogue and the most impressive critical and commercial success of their career". At one point, it was ranked as one of the top five best-selling albums of all time.  Led Zeppelin IV received overwhelming praise from critics. In a contemporary review for Rolling Stone, Lenny Kaye called it the band's "most consistently good" album yet and praised the diversity of the songs: "out of eight cuts, there isn't one that steps on another's toes, that tries to do too much all at once." Billboard magazine called it a "powerhouse album" that has the commercial potential of the band's previous three albums.  Robert Christgau originally gave Led Zeppelin IV a lukewarm review in The Village Voice, but later called the album a "genre masterpiece", and wrote that it showed the band at the pinnacle of their songwriting. Even though he found their Medieval ideas limiting as usual, he said that it is "the definitive Led Zeppelin and hence heavy metal album". In his review for AllMusic, Stephen Thomas Erlewine credited the album for "defining not only Led Zeppelin but the sound and style of '70s hard rock", while "encompassing heavy metal, folk, pure rock & roll, and blues". In his album guide to heavy metal, Spin magazine's Joe Gross cited Led Zeppelin IV as a "monolithic cornerstone". BBC Music's Daryl Easlea said that the album made the band a global success and effectively combined their third album's folk ideas with their second album's hard rock style, while Katherine Flynn and Julian Ring of Consequence of Sound felt it featured their debut's blues rock, along with the other styles from their second and third albums. Led Zeppelin's Rock Hall biography described the album as "a fully realized hybrid of the folk and hard-rock directions". Music journalist Chuck Eddy named it the number one metal album of all time in his 1991 book Stairway to Hell: The 500 Best Heavy Metal Albums in the Universe.

Answer this question "What did some of the positive reviews say?" by extracting the answer from the text above.
but later called the album a "genre masterpiece", and wrote that it showed the band at the pinnacle of their songwriting.