No, it’s not reading a dirty or muddy book.
Dirty read happens in database processing when one transaction can change value and another transaction can read the same value before the first transaction is committed or rolled back. In this case, there is a possibility the first transaction roll back causing the second transaction to read invalid value.
Although there is a way to set a database to disallow dirty read, the process degrades performance of an application because of locking overhead. It also decrease system concurrency.