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a conclusion just restates your first paragraph
its up to your individual creativity in your writing style. starting with "in conclusion.." is one way although it is not the most orignal way to write a concluding paragraph.
what is important is, what is the point you wish to state in your concluding paragraph. it can end with you telling the reader your personal preference (eg. In my opinion, I still prefer the vivid description of the book compared to the...). or you can leave it to the reader to decide what they prefer (eg. Both the movie and book are great in its own way.... ).
bottom line is, you don't have to start with "in conclusion", but there's nothing stopping you from doing so too.
As stated above...
There are many similarities/differences...
A conclusion paragraph starts out with the thesis statement from the introductory paragraph rewritten. After the rewritten thesis statement, summarize the body of the paper in a about four or six sentences.