Plurals using the verb 'be' using There + Be

(a) There is a book on the shelf.
(b) There are some books on the shelf.

The subject follows be when there is used. There is called an expletive.

Notice that the constructions there is and there are can be used to introduce indefinite subjects only.

There is a book on the shelf (This can be the first time that The book is referred to)
There is the book, on the shelf (The book refers to a book that has already been spoken about)

Singular verbs with two or more objects

Sometimes in informal English a singular verb is used after there when the first of the two subjects connected by and is singular.

Eg. There is a pen and a piece of paper on the desk. (informal)
Formally, however, the sentence There are a pen and a piece of paper on the desk is considered to be correct.