I am looking for some place that has an issue-by-issue summary of Sandman. Could anybody provide me such a link?
There's a summary at Neil Gaiman's site but I don't know if that's granular enough for what you want.
Ralph Hildebrandt's page has lots of info about each paperback including a brief synopsis of each issue contained in that volume.
There's also the beginnings of an issue by issue reread of the whole sequence over at Tor's website by Teresa Neilsen Hayden but it appears to have stalled after just one post 18 months ago.
Hy Bender's The Sandman Companion has quite detailed summaries of the original ten "Sandman" collections, followed by analysis and interviews with Gaiman as well as the artists. I refer to it frequently, and own it in hardcover.
The following text is a good summary of the book, taken from this page:
... The Sandman Companion is an essential supplement, or concordance, to the series. Gaiman's stories are thick with mythological characters and references from around the world. He also pays constant homage to his favorite authors, films and books, and he is a devil at hiding clues and foreshadows of future stories in earlier issues. Author Hy Bender is exhaustive in searching out these intricacies of Gaiman's work and does an excellent job of putting them all into context.
The book itself [gives] a brief but exacting synopsis of each story cycle, followed by a "Some Things Worth Noticing" section in which he ties together story and character threads. An in-depth interview with Gaiman himself follows in each chapter, where Bender's well-researched and thoughtful questions are answered by Gaiman with a tremendous amount of insight and wit.
This book: Prince of Stories: The Many Worlds of Neil Gaiman maybe the one you'll really like. It discuss all the sandman volume series and includes information on the characters. Also it covers most of Neil's work.