Actually just to clarify, this book is mainly a series of short stories that connects one of the charatcers from Lord Valentine's castle BUT does little to progress the story of the main charatcer from Book 1.
Therefore you can actually in this case read that book before getting Lord Valentine.
You will also find in the majipoor books that not all are direct sequels to previous books as they jump around 1,000 years at a time to different Lords in charge of the city.
Here's a comment on Book 2 from the silverberg website:
This the second book in the series begun with
Lord Valentine's Castle. This is a
collection of stories set on Majipoor connected by short interludes with Hissune (one of the characters from Book 1). As the copyright page says: Portions of this book have appeared in somewhat different form in Omni, Fantasy & Science Fiction, and Isaac Asimov's Science Fiction Magazine. It adds some interesting details to the history and geography of the big planet, but does
not really further the story of Valentine.
Cheers....