How many of the Heroes of Olympus books are there?
5
5
5
5
5
4
5
4
3
5
4
7
3
6
5
4
7
3
6
5
4
7
3
6
5
4
7
3
6
5
4
7
3
6
5
4
7
3
6
5
4
7
3
6
5
4
7
3
6
5
4
7
3
6
5
4
7
3
6
5
4
7
3
6
5
4
7
3
1
6
5
4
7
3
1
6
5
4
7
3
1
6
5
4
8
7
3
1
6
4
8
7
3
1
6
4
8
7
3
1
6
2
4
8
7
3
1
6
2
8
7
3
1
6
2
8
7
1
9
6
2
8
1
9
2
8
1
9
2
8
1
9
2
8
1
10
9
13
2
8
1
10
9
13
2
12
8
1
11
10
9
13
2
12
8
1
11
10
9
13
2
12
8
1
11
10
9
13
2
12
8
1
11
10
9
13
2
12
8
1
11
10
9
14
13
2
12
8
1
11
10
9
14
13
2
12
8
11
10
9
4 Books