Every year, upon beginning parshat Shemot, I am struck by the same thing. The first few lines repeat things we already know from Sefer Breishit. But the style is different - extremely concise and abrupt relative to the original story. Here are four examples.
"Yaakov, him and his household came." (Shemot 1:1)
"They took their cattle, and their property which they acquired in the land of Canaan, and came to Egypt: Yaakov and all his offspring with him. His sons and grandsons, daughters and granddaughters and all his offspring, he brought with him to Egypt." (Breishit 46:6-7)
"These are the names of the sons of Israel, who came to Egypt: [...] Reuven, Shimon, Levi, Yehudah, Yissachar, Zevulun, Binyamin, Dan, Naftali, Gad, Asher. All those who came out from Yaakov's loins were seventy people, and Yosef was in Egypt." (Shemot 1:1-5)
Breishit 46:8-27 lists every son and grandson, categorizes them by mother, counts them up, and eventually reaches the total of 70 people. This whole process takes 20 verses.
"Yosef and his brothers and all that generation died." (Shemot 1:6)
Breishit describes Yosef's death, mummification, burial, and the oath his brothers made to eventually return his body to the land of Canaan. That, and the death/burial of Yaakov which is not even mentioned here, essentially fill a whole chapter (Breishit 50).
(It's interesting, by the way, that the Egyptians mourned Yaakov for 70 days, but not Yosef. Presumably they mourned Yaakov out of fear of Yosef. But when Yosef died there was nobody to fear. And since Yosef took their land, they weren't genuinely upset by his passing.)
"A new king arose over Egypt, who did not know Yosef." (Shemot 1:8)
From the one word "Yosef", we are supposed to have in mind all the events of parshat Miketz and Vayigash. The verse does not even say something like "the doings of Yosef", but just "Yosef".
(Actually, you could argue that "yada" implies a relationship rather than factual knowledge, so "the doings of Yosef" is not appropriate here. But that just begs the question of why Pharoah chose to reject the relationship so dramatically - a question which is answered nowhere.)
Why this incredible conciseness? I think its purpose is to indicate to us that we now telling the story of a nation rather than of individual people. Occasionally (as with Moshe in chapter 2) an individual's story is of crucial relevance to the nation. But when that is not the case, the narrative has no patience for individual stories. So it minimizes them or omits them entirely, and makes clear to us that it is doing so.