When describing a strong level of interest in a particular subject or activity, there are a variety of synonyms one might use instead of "really into." Some options include "passionate about," "obsessed with," "enthusiastic about," "devoted to," "hooked on," "immersed in," and "fascinated by." Each of these alternatives can convey a slightly different connotation, depending on the context and speaker's intentions. For example, "obsessed with" might indicate a more extreme level of interest than "enthusiastic about." Choosing the right synonym can help to add depth and nuance to one's communication, allowing for more precise and nuanced expression.