r – Unknown or uninitialised column

I have the below warning; due to which I am facing errors while executing the code.

Unknown or uninitialised column: total_books.

###books is my data frame

book_publishers <- summarise(group_by(books,publisher), total_books = n())
book_publishers
book_publishers<- drop_na(book_publishers)
book_publishers <- filter(book_publishers, total_books>250)
book_publishers


book_publishers <- arrange(book_publishers, desc(total_books))
book_publishers 

book_publishers$publisher <- factor(book_publishers$publisher, levels = book_publishers$publisher)

book_publishers<- mutate(book_publishers,
               cum_count = cumsum(total_books),
               rel_freq = total_books / sum(total_books),
               cum_freq = cumsum(rel_freq))
book_publishers

I tried comparing to compare with the expected value

if (random_house_total == 2607) {
  cat("Total books for Random House match the expected value.\n")
} else {
  cat("Total books for Random House do not match the expected value.\n")
  cat("Expected: 2607\n")
  cat("Actual:", random_house_total, "\n")
}

o/p: Total books for Random House do not match the expected value.
Expected: 2607
Actual: 0

This is beacuse, the ‘total_books’ is not initialized

Can I get some help in understanding and resolving the issue?