How many books are in C.S. Lewis' Space Trilogy?
3
3
3
3
3
3
3
3
3
3
5
3
4
5
3
4
5
3
4
5
3
2
4
5
3
2
4
5
3
2
4
5
3
2
4
5
3
2
1
4
5
3
2
1
4
5
3
2
1
6
4
7
5
3
2
1
6
4
7
5
2
1
6
4
7
5
2
1
6
4
7
5
2
1
6
4
7
5
2
1
6
4
7
5
0
2
1
6
4
7
5
2
1
0
6
4
7
5
2
1
6
4
7
5
2
1
6
4
7
5
2
1
6
4
7
2
1
8
6
7
2
1
8
6
7
2
1
8
6
7
1
9
8
6
7
13
1
12
9
8
6
7
10
13
1
12
9
11
8
6
7
10
13
1
12
9
11
8
6
7
10
13
12
9
11
8
6
7
10
13
12
9
11
8
6
7
10
13
12
9
11
8
10
13
12
9
11
8
10
13
12
9
11
8
66
66
144
132
123
144
132