What is the value of first edition Somerset Maugham?

It's not possible to answer this question directly, but I can explain how to go about finding out. You need to bear in mind:

• It will depend on which Somerset Maugham book it is. As he became more famous and his writing skills were recognised, the print runs for the first editions of his later books would have been longer, meaning there are more of them about and consequently the values will be lower.
• It will depend on the condition of the book. Books which are complete, unmarked, and look as if they have not been read are going to be worth a good deal more than those that are well-thumbed.
• If the book has been signed by the author that could increase its value.

If you go to the Abe Books website* (see related links) and search for your book then you can see what various booksellers are offering to sell it for. This is of course more than they would pay you for your copy as they will want to make a profit on the deal.

Searching for your book on the Amazon marketplace may turn up some very high prices. Do not be misled by these as some sellers offer for sale books they do not have, but which they believe they can get if somebody is prepared to pay their asking price.

*I am not associated with Abe Books or any bookseller advertising there. At the foot of the Abe Books web pages is a list of their sites in various countries and you may wish to use one of these.