Starry Starry Night (Time Passengers Series) by D. K. Till

2120 – The USA has disappeared, security robots roam everywhere, and cars are a thing of the past. Tree and her boyfriend, Glim, like all citizens of the new nation of Normerica, live in dorms and travel in flying autopods. Glim has perfected the science of time travel, and they set out to explore the future and the past. Curious about an ancient murder that impacted Tree’s family, they travel back in time in hopes of altering history. But Tree suspects there’s more to the story when Glim starts behaving oddly. So she follows him into the past. What she finds there flips her world upside down. If she returns to her home year, her very life could be at risk. Will she stay trapped in the past, or will she find a way to escape the peril awaiting her?

2019 – Paige Ferguson and her husband, Kyler, are enjoying life as newlyweds when they learn she is pregnant with twins. Her new friend, Katrice, offers a fun diversion when she asks Paige to read her time-traveling story. When Katrice disappears, Paige’s search for answers cause her to question everything she thought she knew about her friend. Who was Katrice? A dabbler in the dark side of life, or an ordinary girl who fell victim to a dangerous villain? A serious pregnancy complication threatens Paige’s future with Kyler and her babies. Will she survive childbirth, and will she ever see Katrice again?