Kathy read 288 pages of her 603-page novel in 9 days.

How many pages per day must she now read in order to complete the book and return it within the library's
14-day deadline?

Kathy has 603 - 288 = <<603-288=315>>315 pages left to read.

Therefore, Kathy must read 315 / 5 = <<315/5=63>>63 pages per day. Answer: \boxed{63}.

To find how many pages per day Kathy must now read, first, we need to determine how many pages she has left to read.

Given that Kathy read 288 pages in 9 days, we can calculate the total number of pages she has left:

Total pages in the novel = 603 - 288 = 315 pages

Now, we need to divide the number of pages she has left by the number of days remaining within the library's 14-day deadline:

Pages per day = 315 / 14 = 22.5 pages per day

Since Kathy cannot read a fraction of a page, we can round up the number of pages per day:

Kathy must read approximately 23 pages per day in order to complete the book and return it within the library's 14-day deadline.

To find out how many pages per day Kathy must read in order to complete the book within the 14-day deadline, we need to calculate how many pages she has left to read.

First, let's find out how many pages Kathy has already read:
Kathy read 288 pages in 9 days.

So, the average number of pages Kathy read per day is 288 pages divided by 9 days:
288 / 9 = 32 pages per day

Now, let's calculate how many pages Kathy has left to read:
Total pages in the book = 603 pages
Pages Kathy has already read = 288 pages

Pages Kathy has left to read = Total pages - Pages Kathy has already read:
603 - 288 = 315 pages

Since Kathy has 14 days to complete the book, she needs to read 315 pages during this time.

Finally, let's calculate how many pages Kathy must read per day to complete the book within the 14-day deadline:
Pages per day = Pages left to read / Number of days left:
315 / 14 = 22.5 pages per day (rounded to the nearest whole number)

Therefore, Kathy must read approximately 23 pages per day in order to complete the book and return it within the library's 14-day deadline.