Simple ADO Recordset, Run Time Error: 3709

Hello Experts,

I am having trouble with what I think is a simple ADO recordset. I am simply trying to count the number of records.

This code works fine:
Dim rstBooks As New ADODB.Recordset

    rstBooks.Open "SELECT * FROM [Books] WHERE [CategoryID]=2", CurrentProject.Connection, adOpenStatic, adLockReadOnly

    MsgBox rstBooks.RecordCount


HOWEVER, when I modify the code so that I can type in the CategoryID from a InputBox
the code fails on the "rstBooks.Open" line.  "RunTime Error: 3709 The connection can not be used to perfrom this operation. It is either closed or invalid in this context.".
Here is the code that fails:

Dim rstBooks As New ADODB.Recordset
Dim intWhatCategory As Integer
   
    intWhatCategory = InputBox("What Category: 1,2,3 or 4")
 
    rstBooks.Open "SELECT * FROM [Books] WHERE [CategoryID]= " & intWhatCategory & ", CurrentProject.Connection, adOpenStatic, adLockReadOnly"
   
    MsgBox rstBooks.RecordCount

I have used the syntax: " & VariableName & "  in other procedures before and it works fine. Why is it failing now?

Thanks!