The book is an allegorical tale about the title character Siddartha’s quest to find meaning in life. I won’t actually comment on the book anymore than that, because I believe it’s the sort of thing where if you’re going to take something spiritual from the reading, you’re better off approaching the material fresh without someone else pushing their interpretation of the meaning onto you.
I would add have also added a word of advice concerning the way to read this book, which is that I would like it first to be read rapidly in its entirety, like a novel, without the reader forcing his attention to much or stopping at difficulties which he may encounter in it, simply in order to hae a broad view of the matters I have treated in it. And after that, if the reader judges that these matters merit examination, and is curious to know their causes, he can read the book a second time, in order to notice the sequence of my reasonings. – Descartes, “Letter from the Author,” The Principles of PhilosophyI think Descartes advice above is excellent advice for reading Siddartha. But if you do finish the book and want to enrich your experience and understanding of it, then you can find yourself a copy of the book I consider a must have for any skeptic, Doubt: A History (previously the Daily Doubter 2005 Book of the year) and flip to the section on the philosophy of the Buddha. Reading that will add another level of depth and appreciation to the novella.