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 :)

Hello Minh , swell is a word we use here to say nice , awesome or kind. Something along those lines I would imagine , although it's not commonly used in todays generation. A lot of use out of them is referring to whatever it is that the Dad allowed them to use , I'm not sure what that's referring to because it's not in your context. He is implying that the "things" the father allowed them to have are going to be used very often , they will get "a lot of use."

Oh. The text is in the Hardy boys series, and this is "the tower treasure", I guess it is old story. Can you suggest me the new American story which you like?

The word "swell" in this sense has seldom been heard in the past fifty years, except in movies set in the past.