Minh, it is ok to read a book series such as 'The Hardy Boys', as long as you understand that, if you are reading the original series from the 1920s-30s, you will encounter some word usage and idioms that are no longer heard today. The word 'swell' is a good example. It is still used in its real definition, e.g. to describe an enlargement of the body due to injury -- "... his sprained ankle began to swell."
In your example, "It sure was swell ...", it means 'really good', and there have been many words that have come and gone since then to replace 'swell' in our daily language. When I was a kid (many many years ago), we used words such as 'neat' and 'cool' (which is still used, sometimes). Today, 'awesome' seems to be THE word, although I am not always up-to-date with pop-culture. There are also regional favorites -- in the American northeast, 'wicked' is (was?) very popular.
The other phrase, '... get a lot of use out of ...', is still used today -- meaning that something will be needed and used often in the future.
I know the Hardy Boys stories have been continued and modernized through the years, right up to a 4 volume series called "Hardy Boys Adventures" in 2013. You could spend your life reading the 100s of stories written over the last 90 years :)
Have you heard of the Nancy Drew series? It is a similar mystery series intended more for young girls, started in the 1930s and continued as recently as 2004. There was even a "Hardy Boys/Nancy Drew Mysteries" TV series from 1977–1979. If you can get to YouTube, you can watch some of those shows starting here: http://www.youtube.com/watch?v=7bGxx8ZHFeU
There are no subtitles for you, but you can practice your English listening skills.
Good luck, and keep READING :)