Read it. Just read it.
Despite his plots being aimed at the YA category, the books are amazingly appealing. I shall be honest upfront and let you know that I haven't read The Screaming Staircase, but I managed to lay my hands on this beauty and its been worth every penny I spent on it.
The plot and its flow is pretty much along the same lines as all his books (I'm assuming Ptolemy's Gate and The Screaming Staircase are along similar lines as the other books): there is a mystery doing the rounds in a parallel London setting, which in this series is, is replete with ghosts, as numerous in variety and as well-studied as types of butterflies in the current day. The Detection Agencies (along the same lines as the Ghostbusters or the Supernatural duo of Sam and Dean) try to rid sites of the ghost infestation through their agents, who are predominantly kids and youngsters. Antony Lockwood's agency is a trio consisting of, besides himself, Lucy Carlyle and George Cubbins. This plot revolves around a potent artefact and a psychotic ghost and how the three young agents try to contain the mess. Pretty straight-forward as it goes, which perhaps makes it easier to concentrate on the characters and the speech.
The characters are well covered and I guess for those who have already read The Screaming Staircase, there is nothing new in that field. The malign ghost is however nowhere near as brilliantly described as Honorius in The Golem's Eye and the Government authorities not depicted as a scheming, corrupted group of bureaucrats, though in all probability, they are all that and more. The story moves at a steady trot and the dialogues are crisp as usual. The final showdown is typically a mix of mad action and last-minutes saves and by the time the book wraps up, there are tantalising tid-bits leading to the next instalments. Put briefly, its a blockbuster kind of a book.
The cinematic treatment of the story makes it all the more fun to read (I hear The Screaming Staircase is already up for a screen adaptation) and I wish someone would make a TV series out of it - one chapter a week !
Either way, do not wait for the screen version; read it up ! Despite dabbling in the supernatural, Stroud has a way of humanising everything and that makes for a rather relaxing read in any state of mind.