How many books are in Connie Willis' Doomsday series?
4
3
3
3
3
3
5
3
4
2
5
3
4
2
5
3
4
2
5
3
4
1
2
5
3
4
1
2
5
3
4
1
2
5
3
4
1
2
5
3
4
1
2
5
3
4
1
2
5
3
4
6
7
1
2
5
3
4
6
7
1
2
5
3
4
6
7
1
2
5
3
4
6
7
1
2
5
3
4
6
7
1
2
5
3
4
6
7
1
2
5
4
6
7
1
2
5
4
6
7
1
2
5
8
4
6
7
1
2
5
8
4
6
7
1
2
5
8
4
6
7
1
2
8
9
6
7
1
8
9
6
7
1
10
8
9
6
7
1
11
10
8
9
6
7
11
10
8
9
6
13
12
7
11
10
8
9
6
13
12
7
11
10
8
9
6
13
12
7
11
10
8
9
6
13
12
7
11
10
8
9
6
13
12
7
11
10
8
9
13
12
11
10
8
9
13
3 books
4 books
2 books
5 books
3 books