It is possible that the Key of Solomon inspired posterior works like the Lemegeton, also called The Lesser Key of Solomon, but there are many differences between both books. The only thing that might have inspired the Lemegeton are the conjurations and rituals of purification, and in a less important way, the clothing and magic symbols.
The Key of Solomon, divided in two books, contains the conjurations and invocations to summon spirits of the dead (preferably in battle) and spirits from Hell (not specified whether demons or punished souls, but it is understandable from the purpose of the texts that those spirits are demons), and to protect the conjurer (called exorcist in the book) from them and against an attempt of possession. There are also curses to oblige reluctant spirits to obey.
The book gives details on how to prepare the ink to draw the magic symbols necessary for the experiments [sic] the magician is going to perform, using animal blood mixed with other substances. All substances needed for the magic drawings and amulets are detailed, as well as the means to purify and prepare them.
The conjurer must also purify himself before intend an experiment, and these rituals are also detailed, as well as the clothing he must use, the colours, etc.
According to the Key of Solomon animals must be sacrificed as offerings to the summoned spirits as a sine qua non condition, what is usual in mediaeval books on black magic.
The book contains instructions to practice necromancy, experiments of invisibility, to cause harm to others, etc., and the zodiacal time appropriate for each experiment.
As a curious need, the conjurer must manifest that he is free of any evil action before intend any of these experiments (many of them to cause evil), and invoke the protection of God.
All magic instrumental needed to perform the experiments is detailed, and also the form to make it.
Unlike other similar books, the Key of Solomon does not mention any of the seventy-two spirits constrained by King Solomon in a bronze vessel as Pseudomonarchia Daemonum (16th century) and the Lemegeton (17th century) do, or the seal of the demons. This book does not give any description of the appearance or specific work of any demon, but only the necessary drawings to prepare each experiment.
According to the text, the book seems to have been written during the Middle Age and not before. During this epoch many books attributed to King Solomon were written, and this might be due to the influence the Crusades and the contact with Jewish kabbalists and Arab alchemists had on European magicians and demonologists.